Also, if you honestly believe every last one of your reviews will be a 5 you may want to look at another business. 

This is one of those, as is the neighboring properties (all of which operate as duplexes, though officially are noted as SF).

Is this a new tenant you put in or did you inherit this one?

Cut to three or so months later... one of my real-estate-friends nudged me to go look at it—the day that it was dropped 50k in price, from 500k to 450k.

When a tenant moves out, transfer the deposit back to Checking so it's ready to apply towards expenses or to refund to the Tenant.If you end up with excess funds in the Checking account, I recommend you transfer it to a third account that is specifically designated for future investments.

The second and third floor is a 4 bedroom, 2 bath apartment which I would live in.

Would I just handle the payments myself as servicer or are there any third parties who specialize in this?

Haven't heard of it, but why not pitch your idea to a few and see if one is open to doing a one-off?

from a laptop or mobile phone on one of my SFR's (internet must be hooked up, but most tenants do it anyway and like to be able to monitor the outside of the house remotely, even if there's nothing going on.)

If you can find one its Millions of dollars since those types of spaces ar3e close to beaches here.