My question is, what should I look for in seller financing, ask about, avoid, would I use the same PSA as a regular purchase, etc.

Make sure that they will return your phone calls promptly.Track all of your income and expenses in report form and review them regularly with a few others you trust and want to see you succeed.  

Just regular mail since you don't have an office is fine.

Most of our house is kept fairly cool but we regularly turn on a gas fireplace to warm up a room we spend most of our time on.

Talk to an Attorney for legal advice. 1 additional thing you could do is puut up Cameras in your house so you can monitor them while they are in your unit. 

Put in good products and do regular inspections and twice a year HVAC servicing and you will minimize issues.3) This is taken directly from my lease.

Monitors.

It’s been almost a year since you posted this, but I’m wondering if you guys do anything on the regular now?

After THAT, you'll also have a regular inspection contingency in your offer.

Even if your 'self employment income' is small, say you do 5K worth of consulting or contracting 'on the side' to your regular w-2 job.