I bought cheap saddle bags because I couldn't pass up the price and I think I can make them work for my bike but is there a way I can make ghetto brackets to hold them down?
Look for anchor points around the rear fender - turn signals, pillion seat, etc. The idea is to keep the saddlebags out of the wheelwell. Look online for pre-made brackets and see where they anchor.
I prefer the term custom made to ghetto. Most brackets are nothing more than a piece of round bar that has been bent, with the ends squashed flat and drilled for holes. Their purpose isn't to hold the bags down, but to keep them out of the rear wheel and drive system. They also prevent rubbing on other parts. Depending on the bike, you could get away without them. While not recommended, I have done so for years (at the expense of some worn chrome). Even cheap bags come with tie-downs of some sort. Just make sure you don't tie them to a moving part, such as the swingarm.
Angle iron, 1 inch thin wall tubing, big hammer, drill and maybe welder can do a lot of bracketing. As other noted- look for bolts already available but a flat fender bracket can be drilled. A rear foot peg can get a flat part of angle iron put on under peg and other end by license bracket for cross piece can be usable- has been don a couple times
