People buy impulsively. Make it easy for people to buy art from you. Get a Credit Card system.
How much cash do you walk around with? Probably not much. Here, in the United States, in 2011, many of us have debit and credit card and that's how we pay for gas, lunch and even parking meters. We don't walk around with a checkbook.
If you're serious about selling, don't make it hard on your clients.
At AvantGarb, we create custom mascots. It took me a long time to get a credit card system. I thought I was too small to need one. Fortunately, I work with pushy people in advertising, PR & marketing who speak their mind with force and clarity.
Once, many years ago, one of those pushy people asked what kind of business I was running - if I didn't take credit cards. I took offense for a day. The next day I made bunches of calls - to my bank, to other artist friends, and I got something set-up with Cambridge Payment System. I have a wonderful consultant there, Lois Jennings, who checks in with me pretty often.
I'm a happy mascot maker, because with a credit card system, it's easy for clients to pay AvantGarb.
...and when AvantGarb gets paid, everybody gets paid.
Of course, love makes the world go round, but on time payments are pretty nice too.