Going to the vet should be pretty inexpensive. It's probably roundworms but you would want to confirm that before any treatment. If your pup is vomiting worms the infestation is severe at this point and your pup should be looked at, it''s heading towards serious and much higher vet bills and repercussions.
After an exam and the right meds in the right dosage, both inexpensive you will probably just be able to pick up your next dosages when they are needed without an exam and going in and that's really cheap. Dewormer vet/OTC costs are comparable (and you would need to call your vet before giving an OTC at least to be sure you are doing things correctly) and the ones from the vet are more effective, safer and OTC often results in emergency and those fees so vet can be much cheaper in many cases.
OTC also aren't effective on many parasites (mainly one) and different parasites need different treatment. You can look into low cost clinics in the area or one attached to your local shelter or even ASPCA for something like this. Should be a simple thing to take care of and not high cost regardless of where you go unless things go very wrong or it isn't taken care of soon.
vetmedicine.about.com
After an exam and the right meds in the right dosage, both inexpensive you will probably just be able to pick up your next dosages when they are needed without an exam and going in and that's really cheap. Dewormer vet/OTC costs are comparable (and you would need to call your vet before giving an OTC at least to be sure you are doing things correctly) and the ones from the vet are more effective, safer and OTC often results in emergency and those fees so vet can be much cheaper in many cases.
OTC also aren't effective on many parasites (mainly one) and different parasites need different treatment. You can look into low cost clinics in the area or one attached to your local shelter or even ASPCA for something like this. Should be a simple thing to take care of and not high cost regardless of where you go unless things go very wrong or it isn't taken care of soon.
vetmedicine.about.com