Also, do YOU show the apartment to prospective tenants while the current tenants are living there (with proper notice of course)?

The best advice is to buy something where you want to live, and do the math properly when calculating expenses. 

It is bad enough to reward criminal tenants but not having a eviction on their record impedes the rest of us from properly screening them in the future. 

Fees should be clearly stated, easy to understand, and justifiable.

Are hard lenders easy to get approval or need sell your soul?

What special rules do I need to follow (e.g. proper number and placement of smoke detectors and carbon monoxide detectors) that might apply to a rental property that don't apply to a primary residence, or where can I find these rules?

For the 1031x thoughts you need to talk to your accountant; main question is are your current properties in a 1031 that would make it easy.

What I do when reconciling client accounts is to just make sure that the "bounce" is recorded properly along with the redeposit.

Single family seems to be easy to rent out and I feel like people are more likely to stay longer in single family than apartment.

Perform proper tenant screening if they will be living next to your family.