@David DachteraYes I'm aware that if I buy the 2nd and take back possession of the property I'm taking it subject to the 1st.

I am just trying to give the right background and context.I grew up moving from one rented house to another, almost every 11 months if not more frequent than that.

Is it possible that the new owner has acquired the property subject to the existing note? 

A closing agent who deals with assignments and double closes on a frequent basis is a must.

If the lien is discharged from the property John still owes the amounts due, it is just a lien on the property any longer.If the buyers choose to take title subject to the lien the lien retains the right to foreclose those junior interests until the lien is discharged by being paid or voluntarily released.As a buyer you would want to clear title to the property thus forcing John to deal with the lien.  

It is frequently off by 20% or more.

If you have and the best route is to help him move the property, one thing you can do is a subject-to purchase if his mortgage isn't FHA or VA.

Ok, now that you have taken your initial step, below are some quick links to get engaged.Since you expressed an interest in buy and hold, I added two guides below on this subject, as you wait to be locally connected.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/startherehttp://www.biggerpockets.com/meetSetting up Keyword AlertsHow to Use @Mentions on BiggerPocketshttps://www.biggerpockets.com/ruleshttps://www.biggerpockets.com/inviteshttps://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 many as 8 of those 20 will be great listing opportunities.Also learn to do several types of strategies such as lease options and Subject To purchases.  

IE-FHA 203B with Repair Escrow financing availability is subject to buyer's appraisal.