What interest rate to charge on sale to tenant?

[Rich Thomas]

I have a duplex and one of the tenants is interested in buying it.  They've been excellent tenants for several years and both have good jobs.  I don't mind becoming the bank if the interest is right - for me that would be 8 to 10 percent.

We have not discussed down or term.  Am I thinking too greedy in for a 8  to 10 percent interest rate for 10 years with a balloon?  Or is that about right?  Any help is appreciated.