[rmrfrmrf]

The model that works best for me is a fixed price based on initial scope with additional fixed or hourly billing for 1) tech support and 2) additions to scope or changes that occur after sign-offs.

Hourly billing is great until it comes time for final payment, which is when the client comes back and says "ok, why did x take you 3.267 hours and y took you 4.535 hours. Can we shave off some of this and that, oh, and this, too?" "Ok, this total is a little more workable, but I'll tell you right now that our billing department won't pay a dime more than $z, so you better adjust your rate or take off some more time."

Then you end up getting screwed out of money. This happens even when you do an estimated cost and have clients pay you 50% of the estimate up front. Fixed billing sets the expectations of how much work will be done and what the client should expect ahead of time, so it's a much easier pill for them to swallow when it comes time to pay up.

[lifeisstillgood]

1. Weekly sprints, weekly billing. No cash delivered after 14 days, down tools and call them to say why.