@Ken M. we live in one, it has an attached unit, but with a door that passes through from both units.

There is a catch - the couple wants to 1031 the funds into their sons next larger project which is TBD.

I feel a loss of direction and that makes it really hard for me to focus and build.Do we keep at building a portfolio of small multi family (very abundant in my market, very rare to find anything above a triplex for sale), with plans of selling the portfolio and 1031'ing into larger properties? 

For example, at the start, do you confirm if all persons in the house are aware of your presence, and do you ask if it is OK for you to open bedroom, bathroom and closet doors?

My strategy incorporates asset protection measures like LLCs, specific trusts as well as professional property management to spread risk and ensure quality operations.As well as using tax codes to my benfiitSection 179, IRC Section 162, Cost Segregation and Bonus Depreciation and later 1031 them out for larger projects. 

Adding 1-2 doors this year would be awesome. 

I'm in a team who does these deals and we have a team of "door knockers" who go back weekly till the auction, they file bankruptcy which only delays 3+/- months 100% chance that the lender will as that their mortgage is removed from the bankruptcy they file NOD yet again.   

Do you have a total price range you're looking for, or maybe a cost/door?

A house that's similar, but 10% larger than another usually isn't worth 10% more.

Every little thing in the project should be in writing, even down to the door stops :-) See my tile spec sheet below ...Two problems with your post though - 1) In my experience, most problems come from the customer changing their minds constantly.