I'm a strict buy and hold investor open to light rehab, multi-family house hacking, nicer single-family properties. 

You can write anything you want in a lease agreement, but it ultimately will come down to what the state codes specify are the responsibilities of the owner and the tenants.

The window is up to the code, but there was no record that the previous owner has a permit when the window was installed. how can I start to get a permit?

They take a ZIP code, sales price and sqft to come up with a price.  

A lot of people on BP have used this approach and it is kind of a cheat code to help you get rolling as an investor due to the high leverage you can use. 

I’m a broker in Vieques, PR (zip code 00765) and while sitting in covid lockdown I thought, hey why don’t I start inputting my listings into Bigger Pockets.

I would disregard age of the property, and focus on location, deal, structural problems if any, and whether wiring, plumbing etc are up to code or insurable.Houses built before 1978 have to be rented with a disclosure (and brochure) about lead based paint and the terrifying ramifications of licking the walls.

They are about $125.00 each and I have an app that will allow a code for a potential tenant to view the property. 

These offer flexibility, and underwriting is typically less strict.

Make sure everything is up to code and has permits.