Most of the big companies will collect a monthly fee from you if your license is active.

I've been very helpful to tenants in the past only to have several of them eventually depart with no gratitude leaving damage / trash / unpaid rent which the deposit was insufficient to cover.

The benefit is the ability to use my LLC for protection in a rental arbitrage scenario.So imho, using the LLC and bank account that I have already setup to collect and make payments in return for an established entity is pretty easy decision.

FOr rents, I would use a payment app, I haven't kept up with those for a time, last I knew was Paypal which my kids says is "so forever ago Dad" so i don't know what it is now, some collection of nearly unpronounceable syllables.

I can post a rental listing on the MLS for my self-managing clients and do showings, collect info, etc, but that's where it ends.  

Normally I would think bring in a 3rd party such as another contractor or an inspector but in the case of a contractor I feel like a lot of contractors trash other contractors work, so this may not be helpful and an inspector may not know enough about foundation work for example to know between good and bad quality work.

The law here says it is illegal to open or trash mails/packages that don't belong to you.  

Ignoring that:This will depend on what your purchase contract says about rent prorations and transfers:If the seller owes rent based on actual rent collected, the scenario above is a net zero.

I have looked into contacting a collection agency, hiring a lawyer to file a claim, or just move on.

If you are referring to you and 9 other of your closest friends collectively investing, it is much simpler.