Sometimes I buy a frame for a painting, and I can sell that painting to you with or without the frame. (If you don't want the frame, I will offer a small discount). More often than not, I do NOT frame my paintings prior to selling them.
Good framing is a difficult procedure, and I prefer to leave it to the professionals. The right frame for a picture also depends on where you will hang the picture. For example, if you plan to hang the picture in your living room, and the living room is furnished with very modern furniture and bright paint on the walls, then a brightly painted modern-looking frame may work best. On the other hand, if you will hang it in the library, that may be filled with heavy wooden bookcases and antique furniture; then an ornate, dark wood frame may look better.
There are many good businesses such as Michaels who can put a very nice custom order frame on your new painting. I may be able to help you find someone near you who can frame your art.
You do not necessarily have to frame your new painting. I like to paint my canvases all the way to the border. In many cases, you can hang the canvas as is.