And then your new cost basis would be $520k from the first property plus your extra $80k invested or $600k. 

If you want to retire, you need a paid off house, $500k+ in liquid assets (usually a retirement account or after tax brokerage), and more than 1 source of income (RE, retirement account, social security for those of qualifying age, part time gig, etc.). 

Even though sales usually pick up this time of year, has anyone else noticed a significant shift in their markets?

And bad credit usually equates to a tighter financial situation, so taking on a higher-interest rate loan is a risk for someone like you. 

Termination/renewals conditions are usually spelled out in the lease itself.

That means you would need to refinance, usually with some down (if you don't have enough equity) and a higher interest rate.

Yes they usually still make money, but they would have made more if they had everything lined up before the closing and the work started the day they closed on the property. 

I hate paying extra taxes myself.

You do have a final walkthrough of the property which is usually within 5 days of closing once the property is vacant (it is in the buyers best interest to make sure the property is empty for this) - that is assuming it’s being delivered vacant.

I have also heard that buying new and having a good warranty is worth the extra money.