But I pay some guy $100 to spend 30 minutes digging a hole.

My main reason for selling is the high HOA fees.

Save those PM fees and put them back in your pocket. 

Since Minnesota allows security deposits in the same account as rental income (as far as I’m aware), I’ll most likely just have one account per property. 

You can redeem the ground rent, buy back the land, for a small fee at closing.

Have her pay you $5 per month in rent.

One charges a one-time onboarding fee and lease renewal fees, while the other two don't.

Is the $775K inclusive of the closing costs, transfer tax, land, architectural drawings, engineering drawings, township approvals, legal fees, holding costs (during construction), realtor fees? 

This new property would net me around $11,500 per month, but the net increase would only be around $4,400.

You Rent a House that you can Rent to someone else for more per month for Cash Flow.