Consider both county and city restrictions that may affect certain neighborhoods.

Right now there are no STR restrictions unless you are in an HOA. 

It's a great time to be in development, not necessarily AirBnB in CA due to the ever-increasing restrictions and fire hazard severity zones - but that's still something great to have experience with.

But are their laws that restrict when one is allowed to do a subject to deal? 

To your point about rental restrictions, each building has different rules and restrictions that need to be researched to determine which properties would work for your goals.

Get a feel for the local government, are they growth focused or are they restricting construction?

Regarding moving a mobile home on the land, you'll have to check with your local zoning office to see what restrictions there are on the land (if any) when it comes to removing the older home and replacing it with a newer one. 

Certain lenders could impose limitations or demand that you settle the current mortgage prior to executing this kind of transfer.Make sure your property is adequately covered by insurance.

Case it point, mortgage regulations, professional licenses like doctor's licenses, blue sky laws, accredited investor restrictions, etc.

@Tony Manning depending on the county there are programs to help with the costs, but requires tenant income restrictions.