If that is impossible or prohibitively expensive, I then evaluate a switch to much more efficient heating equipment coupled with a fuel swap (eg: 80%AFUE oil to 96%AFUE gas).

Many of the walls in the house are masonry, so replacing plumbing is prohibitive.

Though flourescent lights can cause deafening pain for Autistics, it has been shown that kids in general [ non-Autistic]develop more headaches and have more difficulty learning than most other lighting.We do sound proofing between rooms which everyone likes [especially apartment dwellers] We prohibit the use of nasty cheap fragrances.We also utilize "interaction badges" They are a clear card holder on a lanyard.

Many states prohibit advertising properties you do not own unless licensed in that state.

Can I prohibit smokers from renting one of my apartments, or ask if they are smokers when screening tenants?

Payoffs for vacating for such tenants might be prohibited, as is sometimes the case with seniors, those on disability or Sec8.

An SDRP can be invested in "anything that's not a prohibited transaction", per the IRS tax code.An IRA or 401(k) LLC gives you checkbook access to your retirement funds so you can invest without needing to direct a custodian.That's an over-simplification, of course.

When it comes to IRA or 401k you are considered to be disqualified person, as such the IRS rules prohibit you to receive any benefit from your IRA directly or indirectly, providing to your IRA any services goods or facilities or otherwise be engaged in any transaction with your IRA. 

Ideally if I could get them all with one company on one policy it would be best, but the different States will probably prohibit that.

Paying rent is not a choice, and most states prohibit tenants from withholding.I also had a tenant that faked a robbery, claiming the rent money was stolen from the house.