One of my tenants does this but in a non creepy/annoying way.

This property it wasn't kept up with in a while.

Anyone been in a similar situation?

Have the tenants take and send pictures of any maintenance items and video chat with the repair person as needed.If you ever get in a situation where you just feel like you can't do it or don't want to do it, you can always put a PM in place at any time. 

Similarly, if you put several Class D tenants in a Class A 4-plex, what do you think will happen to the property?

I will probably sell the house in a few years since it was built in the 60s and the plumber said that i shouldn’t have any issues for some time now, hopefully.

(Remember - No such thing as a dumb question)And don't be in a rush like most young wanna-be investors...I can't tell you how many times I've seen/heard "I want to have 10 properties within 5 years and be making $100k per year".

Cash for keys is definitely the best way to get people out in the day when I was very active at court houses steps cash for keys was by far the best way to get folks to move and bad tenants in a state with bad eviction laws to me would be the preferred method. you simply pay them when they are leaving the house not before.. that works fine and you give them more than 1k .. you make it worth their while..

Can anyone share a breakdown or budget for a similar project in a similar area?

You do not need to set up an entity in a different state to wholesale.