I've had varying success using food as a cheap source of seeds. Most
of the dried peas and beans work. A small packet these days usually
cost over $1. A pound of Fava Beans or whole green peas cost less
than that and they usually work.

This year I used Goya green peas for seeds because that's what was
available at the grocer. They turned out to be about 4' tall, didn't
need support, and not bad in taste or yield. Peas are iffy here
because of the climate. I just had a 3' short row this year. Next
year I might try a whole row.

Seeds from a ripe bitter melon always works. I had no success from
sun dried peppers probably because the seeds were too old. Green
pepper seeds are not matured enough to work.

Fruits seeds work but it that too many years for them to produce
fruit.

Bulk seeds like alfalfa, wheat, barley, etc. from health food stores
usually works for sprouting.