You may also meet someone  that could be a potential business partner. 

One of the risks here is that you can potentially have a nosey/disgruntled neighbor who would go as far as to file a complaint with the local building department.

Alternatively, you could potentially try posting about their swap opportunity on facebook groups or a simple google search of Home Swap websites could also yield results.

More on my first investment, this quadplex is a fixer-upper and has the potential to add 200k+ in equity with about half as much invested.

Your loan probably technically doesn't allow this because there is a "due on sale clause" but I have never heard of a loan being called as long as it's being paid My advice to you would be to screen potential property managers, read reviews then set it up to be managed by them. 

You might also meet someone that could be a potential business partner.

Potentially fix and flips.

We have a potential deal in the works that has a business on the first floor and apartment upstairs. 

So there really isn't a right or wrong path to take.And you'd also have to put yourself in the shoes of a potential acquiring company.  

Yes there are quite a few around 350k, with lesser rent potential