There are several...
prestigious short story competitions you can enter which are free.
The literary journals often give you a year's sub along with their entry fee. It's a good way to enjoy the magazine and help them out.
If you are going for entry fee comps, PM, then choose wisely, or you'll be bankrupt. Which ones have mana and are recognised by editors and publishers?
That limits you to those attached to literary festivals, e.g. The Bridport, those long established ones like the Fish Publishing ones, and ones special to the memory of a famous writer, e.g. The Carver, the Katherine Mansfield.
The other category is those run by small press publishing companies to fill their annual anthology. Sometimes they are free, sometimes not.
It's not a bad idea to keep you writing if you dangle the carrot of comp deadlines. Mark in on your big year calendar the dates of the comps you think you'd like to enter. Give yourself a two month start date and the deadline.
Good luck and happy writing.