Annual 'maintainence' contracts

[ATH]

What do you guys do for folks who want you to check in on their trees every year?

Here are some of my thoughts, but would ike feedback on what works and what doesn't:
*Do you charge a base fee for the annual visit? How much? (I'm thinking $50ish - which probably won't cover the cost of the visit and follow-up report, but hopefully these clients yield a decent flow of continual work...
*Do you have a standing understanding (or contract) like "we'll do any work that needs to be done, then bill you for that." - or do you put a limit on it like "We'll do work that needs to be done up to $500 as needed, and send you an estimate for anything beyond that."?
*Or do you give a bid on any work that needs to be done for these clients before doing anything?
*If you have an agreement to do what needs to be done, do you just have an open-ended contract??

Thanks for any input you can give!!

 

[son of a beech]

I just charge by an hourly rate for check up work. I bid the first assessment accordingly then if its an annual inspection/check up just inform them of my one person hourly rate. If your making them happy, they will call you back.