For example, if you are studying a syndicated Multifamily deal where the plan is to rehab a property, stabilize it, then resell it in five years, you would have to model your direct ownership option the same way. 

Regardless, you get to see someone purchase a home, diagnose the problems, redesign, repair, then resell the home, with a few missteps or unforeseen problems.

Some of the concerns I have will be resell value of the property even tho I am contemplating a buy and hold strategy.

Then you have to find out who is buying this product in bulk and reselling it to retailers such as yourself. 

to help you to find projects and re-sell your finished properties.Perhaps the most difficult relationships are contractors.  

My plan is to add value and then re-sell or re-finance.I was hoping to find a property that was 20 years old or less, but the vast majority of the properties that I see are at least 30 years old and most of them are more than 40 years old. 

I have seen website like www.idealista.com but I have heard also that some banks are reselling properties too.

If you don't want to take the risk of having someone manage the deal for you.. and being in partnership with a bunch of people you don't know never met and to unwind would be expensive.. then just find a really good commercial broker and have them find you a property that a developer has bought rehabbed and is reselling.. no big mystery to it.. a great commercial broker can be a lifelong contact for you and make you a ton of money. this assumes you have the wherewhithal to buy these on your own of course..

Then resells them for 150K, 200K.

In this Spreadsheet I am comparing: OPTION: 1 Conventional Financing for "Buy & Hold" for a Rental  vsOPTION: 2 using "Subject To" and Reselling to a Tenant Buyer OPTION: 1 As a Rental, the Kitchen and Bathrooms needed updating requiring about $5,000 of work in order to be ready to be a Rental.