I started by going around to 5 area newspapers to get coverage, because the concept was new back in 2005.
Our area has a "community shoppers guide", averages about 30 pages, delivered free in every mailbox on Wed. I buy 3-4 line ads in that paper, trying to change the wording to keep it timely. So that is about $24 per month. The guy has a tidy little business, about 50,000 circulation in the 60 mile radius, but what makes it excellent is mailbox delivery, unlike those racks in front of stores marked "Free-Take One".
Finally, last year, I built a ladies model for one of his sales employees, she uses it to go see her business clients. Keeping the script clever, I get 3-8 calls per week, moreso when gas is expensive. Reliable demo rides are usually the deal maker.
I use my computer's printer to print out cards to carry with me, and I print 8 x 11 flyers with pictures, either of bikes built or those state lines I've crossed, put them in all the gas stations.
It will take 2 years or so to build up enough bikes out there to make word of mouth a third source of customers.
My "bike shop" business license only costs about $12 a year, but I make sure to have it, even though I'm paying sales tax on purchases, not charging the sales tax to the customers.
The final thing I did is make a scrap book, with all the newspaper articles and pictures of all the bikes, so they can better choose model/color and accessories.