Some examples of habitability codes are functional toilets, functional sinks, functional smoke detectors and carbon monoxide alarms, weathertight windows and doors leading outside, bathrooms must have a mechanical vent or an easily opened window, a bedroom must have an easily opened window and either two electrical outlets or one electrical outlet and a light fixture and all pipes, plumbing and electrical must be per code.

Furthermore, I believe there are a handful of tax codes/rules when it comes to renting to family members so make sure you're aware of those.

Quote from @Donald Korman: It depends on state laws and local codes. 

@Rachel H.Yes these are 40 year old MH but originally the county said as long as they were brought up to code we would fall under the grandfather status for shared septic.

Would like to connect with PM’s in the 32501 zip code to help me find and screen tenants. 

for a 4 bedroom ,1 bathroom  ,1500 sqf house in zip-code 21216

Or maybe they want a house with a 90210 zip code because that raises their self-esteem.

Newer houses are up to code, but can be more expensive than an older house.

Because this is unpermitted, and he was shut down there is apparently some from of code enforcement case that was opened.

See your local building codes.