thoughts on single tenant NNN leases?

Looking into purchasing a single tenant building,nnn lease, 5 year renewable for 20 year term, 10% increase in rent every 5 years. 8% cap.

I just learned of these, and apparantly I can buy a walgreens, McDonalds, Burger King, etc this way. You own the building and the land, but not the franchise. Apparantly no maintenance/taxes/ or insurance. All of this is covered by the franchise.

Anyone doing this??? Sounds good initially, but a couple of ways I see one can get screwed:

1) Rent increases of 10% every 5 years doesnt sound like much...eespecially if interest rates go up. You could end up with negative cashflow. After 20 years you have only managed to double the rent...sheesh. With the apartment buildings Ive got, rent doubles every 5-10 years...

2) Single tenant is higher risk for vacancy, thought I suspect this is mitigated by the good credit risk of the above companies.

3) Does commercial land like this have much residual value after the franchisee leaves, hopefully after 20 years? There aren't really too many people looking to lease an empty mcdonalds or walgreens building. Its not really a multi-functional building.

Seems like a decent investment for an all cash buyer...unless inflation skyrockets...

Thoughts? Need more money for more cars