Even if he won't sign a new lease, I would simply post this on his door advising him of the new rental rate, take a picture of it, and save it for possible future need if you have to file for eviction. 

They jetted it out, concerned if it will continue to be an issue in the future or not.

Not to mention the possibility of finding a new location to invest in that may have a higher growth rate since I think the current location has plateaued and might have reached it's peak in value at least for the near future.

I would love to connect in the near future.

Any thoughts on the future of this neighborhood that is situated adjacent to Tremont and Ohio City, which have experienced a boom (read: gentrification)?

You're in the right mindset, and you’re already ahead just by thinking about securing your family's future.

Also, with your 10-unit in Oregon under contract, how do you see rates and local bank relationships influencing your future projects?

Document the condition thoroughly for future reference and estimates.If the property is of interest, it’s crucial to have professionals assess potential structural damage, electrical issues, or mold remediation costs.

HELOCs often have variable interest rates, and you can borrow more in the future as you pay it down.If you're looking for long-term stability and want to lower the interest rate, cash-out refinance is probably the better option.

I am interested in getting into real estate investing in the near future (I was thinking about single-family homes).