I've heard that oversizing the AC can lead to humidity issues due to short cooling cycles.

Those might make good rentals...but also there can be extra costs...see if they are in PIDs/PUDs or MUDs that add significant cost to the monthly payment...maybe $100-$200 extra a month.Also $2500 sounds high on rent to me for 1800sqft....I would think more like around $2000/month, but haven't looked in that area lately.I do like Forney....one issue is I don't think there are good demand drivers there. 

She has decided he is using her trash cans, even though there is no proof.   

So the heloc difficulty may be because its not a primary home. but im sure you can find a lender for a heloc.have you tried a DSCR because that way you can keep it in your LLC?

What else can I do to get him out or push the Eviction through Cleveland courts.

Not many coastal markets where you can buy a block home under 100k!

This opportunity fell in my lap as I know the motivated seller who is willing to sell, but I'm not sure if I can get the price that he wants for it.I don't have the property under contract yet, and this is my first wholesale deal.

Honestly there are several career paths that will help (Renovation contractor, real estate agent, corporate RE analyst)  but depending upon whether you are looking for a career investing/flipping versus using your W-2 career income to build more by flipping, you can approach it better in my opinion by learning through doing.Flipping especially 1 at a time isn't a full time job and my thought is that you get help on your first, maybe first few flips. 

You can often hire them at a reduced rate.

Feel free to shoot me a message if I can help any.