Before I can move forward I'd like to get a professional's opinion.

I have tried in the past to do this with a solid written agreement spelling out exactly what the terms of the agreement were, what was to be done, and that the work needed to be completed in a professional, workmanlike manner.

I am aiming towards acquiring a large out of state multifamily deals this year that is large enough to support a professional 3rd party property manager and am "requiring" myself to acquire my first one by the end of this year through syndication.

I am a young professional looking to get started in REI.

I think you will be better served being aggressive in making offers, shopping hard, building relationships with real estate professionals, and in the end tackling a house that you can add value to. 

So, what if I had sold the house and the drain was slow and he required me to fix that problem and I agreed to clean it up and then snaked it before closing - would that absolve me from liability of the actual problem, which now required the old drain pipe to be replaced?

The assignment assigns the Mortgage to youThe allonge transfers the note to youAs for due diligence :Are the notes Dodd Frank CompliantHow much are you investing relative to the current unpaid balance (UPB0How much are you investing relative to the current Value of the propertyAre there unpaid taxes on the propertyAre there any unpaid liens on the propertyAre the borrowers currentHave the loans been professionally serviced so you know the pay history and the correct UPBDo the borrowers pay on timehow long have the buyers been in the property, do they pay on timeAre taxes and insurance escrowedIs there insurance naming the lender is there a lenders title policy

If it gets down to pocket change range for the local professionals and they aren't touching it, there's a reason why.

You can then offset a passive loss. ( I know it is a complicated topic, please talk to qualified professional) 

This will help local professionals find your post and help you with your search.Best,Abel