If your parents will only let you have one horse , it is likely that they cannot afford more than one - so how is it that you think they can afford the associated costs of a foal.
The outlay for a foal over the span of its growing years is , generally speaking , much greater than that of an adult.
Have you also taken into consideration the possible damage to your mare. Are you prepared to loose her should things go pear shaped? Are you prepared for your foal to go to slaughter if you can no longer afford him (somthing that you need to be able to do on your own , IMO , before your breed , so you need your own income NOT your parents) because breeding your mare to a fugly stallion with bad conformation and lack of anything of note in his carreer in his chosen field is basically signing a possible death warrent on your potential foals head. If you at the very least choose a nice stallion , registered , and favouribly done something of note then your foal will at least have the possibility of being registered , will have favorable parentage on at least one side , and as such , will be more appealing to a buyers market should things go wrong.
Also , by breeding to a shoddy stallion you are CHOOSING to set your foal up with physical issues that s/he will carry for life which will make it all the more difficult for him to excel in a job. Why would you inflict that on the foal your so desparate for? If it is your 'greatist joy' to breed your mare , than you should at least do her the common decency of finding her a reputable stallion - not breeding her to anything with testicles that should walk past her fence....
Be a responsible breeder NOT a backyard breeder.