commercial lease for daycare

[John Coffey]

I have purchased a small private school building.  It's about 12,000 sf of classroom, kitchen etc and 4000 sf of gymnasium/workout area.  The daycare is interested in the whole building.  I have priced it to them but said this is just to help you get started and I would need more of a lease payment once you exceed  a certain number of kids.  Any suggestions on what this formula should be?  I'd rather not get involved in someones finances but I need to do something to make it have upside.  I have not given them a lease yet.  Thank you for your time.