Do it yourself shots

We have decided to keep the 3 German shepherd puppies that wandered into our yard (after weeks of looking for the owners). This is a huge responsibility. My 4 adult children still live at home, so the responsibility will be shared.  
Still it's a of money.  So far the "puppies" are going through a 50 lb bag of food in two weeks (thank goodness I work for a Co-op and get a nice discount).  The vet said a puppy pack is 245.00, and this doesn't include getting them fixed.  Wow.  I was going to do the pack, but it just seems to much, for not enough.  My work sells puppy shots, it doesn't seem that hard.  I'm still going to take them to the vet, but think  about worming and shorts myself.
Has anyone done this themselves? Advice, do's and don'ts.
Thanks

In Oregon you can't administer the canine rabies shot. The other canine shots in a puppy panel are available at feed stores.

Just make sure you get the right needle size. I had needles that were for pigs and when I gave the dog a shot he didn't like it so I bought smaller needles and then the penicillin wouldn't even go through the tiny needle. I must figure that stupidness out! I've found giving shots easy, so long as you have the right needle size.

The puppy shots are all in one. They are needles already loaded, no measuring, or worrying about size
They have everything except rabies. That the vet will have to give.

Revival Animal Health (www.revivalanimal.com) has all kinds of vaccines for dogs and cats, among other things. You can just call them and tell them that you want the correct needle size for a dog for vaccination and what vaccines you want as well, and they will direct you.
I have done a lot of research regarding vaccinations over the last 25+ years and would suggest spacing them out as well as not giving 3-way or 5-way vaccines. It is completely unnatural for anyone, dog, cat, or human, for that matter, to have the body exposed to everything at once as is found in the 3 or 5-way vaccines. It is asking a lot for the immune system to deal with such an onslaught of antigens, whether they be modified live or dead. Single-antigen vaccines make a lot more sense, given a few weeks apart, and are much more natural. Revival sells those vaccines as well.
As far as giving the actual vaccine, it is quite easy. Just pick up the dog's scruff a bit and give it into the skin there.
I would also recommend reading more about vaccinations, in general, and perhaps following the vaccination protocol recommended by Jeanne Dodds, DVM. She is known and respected all over the country and has done a lot of research regarding vaccinations. Her protocol can be found all over the internet. Here is one such place: https://www.animalhealthfoundation.org/blog/2017/12/dr-jean-dodds-dog-vaccine-protocol/

Either way, doing the vaccines yourself (except for the rabies as others have mentioned, which must be administered by a veterinarian) will save you a heck of a lot of money. The same is true for any type of deworming you decide to do. As far as dewormers for dogs, fenbedazole, sometimes known as Safeguard, is one of the best ones out there, covering a lot of worms, including whip, hook, and tape worms, and even giardia (not a worm, but a single-celled organism). Fenbendazole is also known to be one of the safest.

Thank you very much Annie, you have been very helpful.