Combo vaccines are given every 3 weeks, usually 6,9,12 and 15 weeks old. You can get them at feed stores/ co-ops. Only problem is how they have been handled. If they didnt get put in the refrigerator in a timely manner and got to warm then the vaccine is no good. If the vet does your vaccines on his schedule and your dog gets sick, the vaccine company will pay the tab, doing them yourself you are on your own.

You can't buy Rabies, it has to be given by the vet clinic. The dog has to be at least 12 weeks old. Dewormers can be purchased over the counter or even at your vet clinic to give yourself. Find something that does hook, round and whipworms.

Heart worm prevention is usually started around 4-6 months. Unless you use ivomec, then you are supposed to have a prescription for any of the other products from your vet. Some online places wiggle through doing that somehow. Some vets will write the script and some won't.

Let me know if you need anything else.