I use all of these - I charge by value for contained projects and per week/month when they are longer, less defined projects with incomplete scope. I ask for 5

I use all of these - I charge by value for contained projects and per week/month when they are longer, less defined projects with incomplete scope. I ask for 50% up front and 50% on completion, and any maintenance is considered retainer which has a fixed monthly cost if they so desire. I do mine for referrals and am still trying to tap through my networks