In regard to selling your quilts on ebay, I will reference another thread in this forum ( http://www.quiltingboard.com/posts/list/889.page ) discussing the fact that many people do not value a quilt as much as quilters do, because the same is true of the quilts sold on ebay. If you sell one there, you will get nothing close to what it is worth, and too many times I have wondered if the seller even covered their actual cost to make the quilt.
In answer to your question, I usually only sell on a commissioned (pre-ordered) basis, with half up front. In the past year or so I've been selling only my quilting services, which I prefer. (I like to quilt more than I like to piece.) One advantage to this is if you get "stuck" with a quilt because the customer changed their mind, you get a quilt out of the deal. You can then either sell it, or keep it. (I make them sign an agreement to this up front.) I have gotten 3 quilts over the past 2 years; 1 of them was because the Dear Lady passed away & her family didn't want the quilt, and the other 2 were from the same person who moved a thousand miles away. She said she forgot about them, and didn't have the money to pay me the balance. I offered to hold them for her & she could pay it off as she could over time. She said ok; that was a year and a half ago. They're still in my sewing room, waiting for her to return. I honestly think, & thought it at the time as well, that having them quilted was a novelty idea to her, more than a true desire to have them completed. (She didn't make them and she had been storing them in the attic. Again, I refer to the other thread.)
Sorry to go on & on, but my point is there is money to be made at times, but there are pitfalls as well, as with anything I guess. :)