If stuffing TP down the commode is entertainment to them, they're not likely to change that voluntarily.My $0.02 ...

Seems like my area is allowed to do STR and I was able to obtain where to contact to, to make sure what I found is accurate. 

I am an investor who just obtained the salesperson license in Massachusetts.  

What are odd of obtaining property doing this?

I don't yet have much experience obtaining seller financing, but I would think that emphasizing the tax benefits is a big one.  

If this seller just renovated, hasn't owned it long and has a mortgage, your chances of obtaining favorable to you proper SF are low anyway.

Can someone guide me where to apply and obtain a license to build this basement unit to an official unit with its address, electric, and other amenities?

If you don't have the liquidity to purchase the property your other option is to finance the acquisition but how do you obtain financing when you can't even show sufficient down payment funds/liquidity on your PFS?

If we can find an investor to help us obtain the property, we have no problems in paying the mortgage just as we've been paying the owner of the property's mortgage for 11 years.

My plan is to obtain a triplex or quadplex and house hack that for a year.