Ill honestly tell you that if you are looking to get 6-6.5% but not have to deal with it anymore, you should simply sell it, and put the money into a dividend fund.
If its mostly already depreciated, further depreciation wont really help you. Additionally, since you are already close to retirement age, it would be a great way to move the money into retirement accounts, and use the additional payments you can make toward said accounts to protect it from as much taxes as possible.
Another thing to think about is potentially adding it as part of your retirement account first, specifically by "buying" it from yourself to yourself, from your actual ownership into the ownership of your 401k.
By doing this, you avoid taxes, especially if its a ROTH IRA.
With many dividend markets ranging from 4-8.5%, the average comes out to be 6-6.25, which is your desired range.
Additionally, the chances of default on the land contract exist, with additional risks of noone wanting the land contract to begin with.
With dividends, they simply exist, and are immediately accessible.
Ultimately, its up to you though.
Ill go ahead and tell you though, anything that I run into that provides me with less than a 10% gain, I drop and put that money into stocks, bonds, and ETFs.