We had a wash & fold service with pickup & delivery, which added complexity to the operation.

@Alecia Loveless is correct--tenants need access 24/7 to their electric service panel, water and heat, assuming those are individual utilities for each unit. 

The fee for this service is basically passed down to the guest one way or another.

If you want to go further, you can use a service like Safely or AutoHost to run background checks.For payments, I’d recommend using a platform like Stripe or Square—they’re secure and easy to set up.

Do they use a servicing company to make the payments directly to the , or do they make payments directly to the seller and hope they pass them on to the lender?

I am a long-term investor, but I also provide services to long-term investors, so my advice is biased toward that option.  

Quote from @Collin Hays: From a macro standpoint, cash flow is difficult when servicing debt, at least in the early years. 

You are not paying for their services and won't cost you anything extra anyways. 

Use a service like TurboTenant or Avail......

At our wealth management firm we have CPA's on staff, we provide overall wealth management services for high net-worth clients.