Ok, now that you have taken your initial step, below are some quick links to get engaged.Since you expressed an interest in Turn Key and Wholesaling, I added the below links for your review, while you wait for others to provide feedback on notes investing.https://www.biggerpockets.com/renewsblog/2014/03/23/what-does-turn-key-real-estate-business-entail/ (Turnkey REI)https://www.biggerpockets.com/renewsblog/2015/01/31/ultimate-beginners-guide-real-estate-wholesaling-2/ (Ultimate beginners guide to wholesaling)https://www.biggerpockets.com/renewsblog/2013/10/31/wholesaling-podcast-mike-nelson/ (BP Podcast 042 - wholesaling) http://www.biggerpockets.com/startherehttp://www.biggerpockets.com/meetSetting up Keyword AlertsHow to Use @Mentions on BiggerPocketshttps://www.biggerpockets.com/ruleshttps://www.biggerpockets.com/inviteshttps://www.biggerpockets.com/forums/categorieshttps://www.udemy.com/biggerpockets-real-estate-investing-course/ (video with 64 lectures and approx 6hrs of material)https://www.biggerpockets.com/real-estate-investing (Ultimate beginner's guide to REI)REI can be very daunting, but, before you go searching for that 1st buy, please take a few minutes to bone up on the tips in link below.https://www.biggerpockets.com/renewsblog/2014/12/19/real-estate-investing-success-smart-tips/REI books suggested by BPershttps://www.biggerpockets.com/renewsblog/2015/11/13/7-real-estate-books-beginner-investors/ (7 absolute must read books for beginner REI)http://www.biggerpockets.com/renewsblog/2013/04/14/best-real-estate-books/?

As in, how do I know that the seller is not simply making it up on Excel and printing it?

Your time here will be well spent.Since you expressed an interest in multifamily units, I added a couple links below for your review.http://www.biggerpockets.com/renewsblog/2014/07/19/how-to-buy-a-duplex/ (guide to buying a duplex) https://www.biggerpockets.com/renewsblog/2015/11/16/how-to-choose-areas-multifamily-deals/ (Choosing multi-family deals)Now that you have made the move, below are some links that will help with the navigation of the site. http://www.biggerpockets.com/startherehttp://www.biggerpockets.com/meetSetting up Keyword AlertsHow to Use @Mentions on BiggerPocketshttps://www.biggerpockets.com/ruleshttps://www.biggerpockets.com/inviteshttps://www.biggerpockets.com/forums/categorieshttps://www.udemy.com/biggerpockets-real-estate-investing-course/ (video with 64 lectures and approx 6hrs of material)https://www.biggerpockets.com/real-estate-investing (Ultimate beginner's guide to REI)Before your 1st purchase, please ensure you visit the below link for some tips.https://www.biggerpockets.com/renewsblog/2014/12/19/real-estate-investing-success-smart-tips/REI books suggested by BPershttps://www.biggerpockets.com/renewsblog/2015/11/13/7-real-estate-books-beginner-investors/ (7 absolute must read books for beginner REIs)http://www.biggerpockets.com/renewsblog/2013/04/14/best-real-estate-books/?

Finally, use all these numbers, including purchase price, repairs, rental income, expenses, and sales price or cash out refi after X number of years (you can play with these parameters) and calculate IRR on the series (can use the excel function to do this) ... this is your total return, over the life of the investment, including ALL sources of profit.

Your time here will be well spent.Since you expressed an interest in wholesaling and flips, I added guides and podcasts below to help increase your knowledge of these niches.http://www.biggerpockets.com/renewsblog/2014/01/07/flipping-houses/ (step by step guide to flips)https://www.biggerpockets.com/renewsblog/2015/01/31/ultimate-beginners-guide-real-estate-wholesaling-2/ (Ultimate beginners guide to wholesaling)https://www.biggerpockets.com/renewsblog/2014/10/09/getting-started-real-estate-wholesaler/ (BP Podcast 091 Wholesaling)https://www.biggerpockets.com/renewsblog/2013/10/31/wholesaling-podcast-mike-nelson/ (BP Podcast 042 - wholesaling)Now that you have made the move, below are some links that will help with the navigation of the site. http://www.biggerpockets.com/startherehttp://www.biggerpockets.com/meetSetting up Keyword AlertsHow to Use @Mentions on BiggerPocketshttps://www.biggerpockets.com/ruleshttps://www.biggerpockets.com/inviteshttps://www.biggerpockets.com/forums/categorieshttps://www.udemy.com/biggerpockets-real-estate-investing-course/ (video with 64 lectures and approx 6hrs of material)https://www.biggerpockets.com/real-estate-investing (Ultimate beginner's guide to REI)Before your 1st purchase, please ensure you visit the below link for some tips.https://www.biggerpockets.com/renewsblog/2014/12/19/real-estate-investing-success-smart-tips/REI books suggested by BPershttps://www.biggerpockets.com/renewsblog/2015/11/13/7-real-estate-books-beginner-investors/ (7 absolute must read books for beginner REIs)http://www.biggerpockets.com/renewsblog/2013/04/14/best-real-estate-books/?

We have excellent property management in place and offer a solid product.  

Ok, now that you have taken your initial step, below are some quick links to get engaged.Since you expressed an interest in flips and buy and hold as well as a love for multifamily units, I added some links below for your review.http://www.biggerpockets.com/renewsblog/2013/01/04/how-to-rent-your-house/ (house rental guide)http://www.biggerpockets.com/renewsblog/2013/02/22/buying-rental-property/ (how to buy a rental property)http://www.biggerpockets.com/renewsblog/2014/01/07/flipping-houses/ (step by step guide to flips)http://www.biggerpockets.com/renewsblog/2014/07/19/how-to-buy-a-duplex/ (guide to buying a duplex) https://www.biggerpockets.com/renewsblog/2015/11/16/how-to-choose-areas-multifamily-deals/ (Choosing multi-family deals) http://www.biggerpockets.com/startherehttp://www.biggerpockets.com/meetSetting up Keyword AlertsHow to Use @Mentions on BiggerPocketshttps://www.biggerpockets.com/ruleshttps://www.biggerpockets.com/inviteshttps://www.biggerpockets.com/forums/categorieshttps://www.udemy.com/biggerpockets-real-estate-investing-course/ (video with 64 lectures and approx 6hrs of material)https://www.biggerpockets.com/real-estate-investing (Ultimate beginner's guide to REI)REI can be very daunting, but, before you go searching for that 1st buy, please take a few minutes to bone up on the tips in link below.https://www.biggerpockets.com/renewsblog/2014/12/19/real-estate-investing-success-smart-tips/REI books suggested by BPershttps://www.biggerpockets.com/renewsblog/2015/11/13/7-real-estate-books-beginner-investors/ (7 absolute must read books for beginner REI)http://www.biggerpockets.com/renewsblog/2013/04/14/best-real-estate-books/?

Furthermore, investors get excellent tax treatment that aren't possible in mutual funds, etc.  

You must take risks, but, ensure that they are calculated risks.Below are some links to get you started. http://www.biggerpockets.com/startherehttp://www.biggerpockets.com/meetSetting up Keyword AlertsHow to Use @Mentions on BiggerPocketshttps://www.biggerpockets.com/rules https://www.biggerpockets.com/inviteshttps://www.biggerpockets.com/forums/categorieshttps://www.udemy.com/biggerpockets-real-estate-investing-course/ (video with 64 lectures and approx 6hrs of material)https://www.biggerpockets.com/real-estate-investing (Ultimate beginner's guide to REI)REI books suggested by BPershttps://www.biggerpockets.com/renewsblog/2015/11/13/7-real-estate-books-beginner-investors/ (7 absolute must read books for beginner REIs)http://www.biggerpockets.com/renewsblog/2013/04/14/best-real-estate-books/?

This is an excellent question.