I was thinking of mailing the two neighbors and asking if they would be interested in purchasing versus someone else (or myself) who would likely build on the land which they have enjoyed vacant for some time now.

I have two tenants that are pretty good tenants but don’t have a lot of money.

I am exploring both short and long term investment as an out of states investor and trying to understand between Cleveland and Columbus OH.I have been learning these two markets are appreciating and have a good cashflow.As I am new to these two markets, I would like to learn which markets are providing a reasonable cashflow while up potential of appreciation for next few years.between these two markets, which ones are suggested?

Offset as much as you can, save up as much as you can, and repeat in a year or two while renting out the previous place. 

Would I be better off keep the two businesses separate?

From the COP's website:Dwelling, Multifamily: A building or buildings attached to each other and containing two or more dwelling units.

We have a similar situation (partnership between two LLCs) and our attorney recommended forming a partnership LLC with the two individual LLCs as members. 

The two of you have to come together in negotiations that work for each side. 

I invested at 18 and  sold my first house two years ago.

If you were to stop renting out a portion of your home and live in the entire property for at least two out of the five years before the sale, you could potentially qualify for the full $250,000 tax-free limit.