@Dan Engberson question #1: how important is it for him to avoid capital tax gains?? Basically he can sell it, pay taxes, and put the money into CD’s, etc. as a safe and simple way to retire. BUT, he will pay hefty capital gains. FYI he may not care, but whoever inherits his assets in the future may care ;)
So if he wants to avoid capital gains, he needs to do a 1031 exchange, which has strict timeframes to adhere to and is a semi PITA to deal with. BUT you avoid paying the tax (for now at least.) Exchanging into another physical property, even if it's NNN, has risk and some management responsibilities, which I think he won't want. Next option is to 1031 into DST funds. These are basically real estate funds, and are usually professionally managed, and it's easy to buy into a few diff ones for diversification. That sounds up his ally IMO. You basically need to research the heck out of the DST market to make sure you're getting good ones, and not overpaying in fees. The 2 big negatives of DST are 1- they're not liquid, so you need to commit for several years before an exit and 2- they have a lot of fees, so the return is usually less than buying your own NNN property. But they are passive and professionally managed.