Not a specialized niche or technique that worked for one person.

I also don't want to assume I can do/change/repair/replace something, only to find out that it's not allowed by code or law and really makes the investment worthless?

Give @Linda Weygant a call, or one of the other CPAs that specialize in RE.

May I ask what your speciality is in accounting ?

You might consider Niche or Specialized Housing like student housing.

The seller is responsible for fixing a few code violations (super small details like locks on doors).  

THIS IS A VERY TRICKLY PROCESS AND THEY REJECT MORE THAN 50% OF W-7 AND THEY HAVE TO BE REFILED....according to my CPA.The tax preparer will need to do a paper filing of the PARTNERSHIP INCOME tax return and it will also be sent to a special unit at the IRS with the investors completed W-7.

You might consider Niche or Specialized Housing like student housing.

Can you serve niche tenants, like some organization, that reduces vacancies or pays premium rents for special amenities or location?  

You might consider Niche or Specialized Housing like student or medical housing.