Considering the extreme seriousness of a possible Parvo infection, the first thing you really need to do if at all possible is to at least obtain an official diagnosis from a Vet to determine if the condition is in fact Parvo or something else. The diagnosis will cost you far less than additional treatment; however the Vet may very well be willing to work out a time payment schedule for you which you might find affordable for treatment. The first thing to do is to make a telephone call and inquire after explaining the symptoms displayed by your beloved dog and your financial situation.
Something to consider as a home treatment, which would be my choice, is the use of colloidal silver which kills both bacteria and viruses. Prior to the development of the pharmaceutical industry and the development of commercial antibiotics, it was used extensively by physicians as a natural and effective antibiotic. An excellent article about its use to treat Parvo, and an accompanying video is at the following Link:
Note that the author recommends a colloidal silver of 10 ppm's (parts per million). However an excellent colloidal silver, which is the choice of many alternative physicians and which I use myself, is MesoSilver which is 20 ppm,s. To read some testimonials about its use go to the above Forum entitled Alternative Therapies
and read my Post, "Colloidal Silver dosage". However, note that the information is for its use with people and not dogs or other animals. You can read more about it here: https://www.purestcolloids.com/mesosilver.php
Also keep in mind that it will still cost you some money just to purchase it. Click this Link to get an idea how much:
Therefore I suggest making that phone call to the Vet as explained above before doing anything else. Remember, veterinarians love animals every bit as much as we love our pets, and their human side, as well as that of their influential office help, can sometimes be very accommodating. Good Luck.