I have just the thing for you!
DarlingMionette's Commission Guide
can walk you through the process. A lot of people prefer to pay with a PayPal account -- there's less private, sensitive information that isn't involved as there would be with cash or checks. PayPal is just a form of buying/selling things online (think bank transfer only with e-mail addresses); a lot of people who buy from eBay have one.
As for $5, I think you're underselling yourself for those portraits. While cheap, you'll find yourself with a huge
order of commissions and you'll struggle to get them all done in a timely manner. Set a limit for now (such as "only 5 slots available, 5 slots for reserve"), and as you finish a commission open a new spot up. This will help you learn to prioritize.
In addition, you don't need photographic references. Some people will ask you to draw their horse, for example, doing an action that they're not in the photo reference(s) they send you. If you'd like, feel free to e-mail me here and I'll gladly give you more advice on the subject, and even some critique if you would like. (:
Also, don't do half-off
. By mandating a "50% down-payment," you're helping insure that you're going to get paid. (So you don't finish the picture and send it off only to hear you won't be getting paid -- they have some sort of excuse.) It also helps to not post the finished product of the drawing
online or mailing it off until the full payment is received. That way, you're not getting ripped off! Communication
is also key. Show the commissioner your sketches (make sure to have your signature[s] on them so they don't take off with that and not pay you, too) and ask if that's how they'd like their commission. Let them know if something happens that causes you to postpone or cancel their order. Refund any money if you have to cancel due to unforeseen circumstances (such as a family emergency).
And last, but not least, testimonies
! If you can get your commissioners to leave a review, you're more inclined to get more customers (especially if you have a good review on your work and the time spent on it).