This tenant's current lease is up in a few months anyway, but how now do I believe in the day where I am no longer involved with this person whom I very much do not want to be renting to anymore (let alone sharing my own home with)?

Did your current property manager place this tenant? 

Use the equity in our current home to build a kitchen in the basement and convert said home to a duplex.

So currently the neighbors grey water mostly goes in my driveway, and there appears to be what used to be a toilet that might be leaking sewage in the basement.The floor drains have collection of water.   

Do you think it's a good money investment considering current crushing market and if you consider this as a safe investment. 

Well I think you should only increase the rent if the current rents are under market value for the condition of the units.

A cash out refinance to buy more property would put a substantial dent in cash flow with current interest rates.

You should only have to change when your current software has a flaw or lacking feature causing you to spend too much work on a work-around.

I'd love to put you in contact with these people and start marketing your services to them, I have done this maybe 40 times now with my current lenders and i typically just add my payment into the HUD and the borrower pays it, this service wouldn't cost you anything.

Good advice from @Nathan Gesner and Account Closed Also bear in mind that if you can find a current deal that makes sense, and will generate even a decent amount of cash flow right now.....then you can just about count on it doing very well once you are able to refinance.