Right now the multi-family market is hot so there are more buyers than sellers, you may have some better opportunities with SFH's.There are some great books out there that will help you such as @Brandon Turner 's 'The Book on Rental Property Investing'.

Your potential buyers should know how to estimate rehab costs all by themselves. 

When the downward economic cycle happens and shifts more to a buyers market then they start buying more.

From what I've read in the forums and have heard on the podcast is that you find a seller who is trying to get rid of their property, and a buyer who is wiling to pay cash for the property.

Landscaping can definitely increase ARV, but may make more of a difference when it comes to first impressions of a buyer/renter. 

A mortgage is where a bank pays money directly to a seller and retains title of the property until the buyer pays back the loan.Because I am not creating a mortgage, I do not have to follow mortgage lending rules.

I always warn my buyers of the risks, but overall, I don't often recommend those certificates are required for sale.

Being able to speak intelligently to buyers and sellers about the local community and market, the up-and-coming areas, etc. always beneficial.

Older homes have more risk, in my opinion, because things may not be level, you many not be able to use standard/bulk items, specialty items cost more, you need to create a space that matches the house period, and the potential pool of buyers who desire older homes is smaller (at least in our area).

At this time I have 2 VERY interested buyers one offering $700K , another offering $710K.