It just depends what you are looking for though.

You don't need to do section 8 to make positive cash flow, but I guess it depends how much positive you want.

It will depend on your budget and if you are willing to take hard money. 

Depending on the zip code I was wondering could I gamble with them on a fix and flip or brrr.

However, this also depends on their ability to prove your neighbor negligent, and the overall cost of the claim.

The DSCR scenario you mentioned doesn't seem too far off depending on the full scenario.

Properties also have specific risks depending on if they are industrial spaces, commercial buildings or multi-family units.

It doesn't hurt to go over the numbers with a lender though who could give a breakdown of what a closing might look like depending on your buy box. 

With 3 properties already, you're definitely not "new" anymore ;-) Doing a refi is very possible (depending on how much equity you've accumulated) to do those types of things...the issue can be the tax ramification that you face if/when you do it.

If you renovate for a flip and then decide to BRRRR you will likely get less than you expect because the finishes will be too nice for a rental (depending on the neighborhood, it could work where you are in that price point).