IMO you will further restrict your renter pool. 

We want to understand how much loan do lendors provide for buying the land and do they have any restrictions for the loan like need to build in 1 or 2 years etc.

So there may be no actual restriction on TCO for residential, but because of the challenges of doing this for residential homeowners they may have internally decided to restrict it to commercial. 

However, locally some places in PA are allowing ADU, but have restrictions that if you build one for a parent or a child, that once they leave it can NOT be rented to a non-relative. 

Make sure you purchase something void of CC&R STR restrictions. 

You want a ratio of 1 to 1, anything higher is more restrictive and can mean you will get less money then you are after.  3.

Would you find a 55+ park to be too restrictive for a 1st time park buyer or would you say if other factors made sense this would be worth considering?

There are rental restrictions and rising crime.

Some neighborhoods had all yellow curbs, and our MTR investor-friendly agent quickly taught us that restricted parking would be problematic (especially with us house-hacking and needing our spots).

Is the land build able or are there title restrictions or land conditions saying it will be forever green space?