it really depends where you live, but here in Ireland, where everything is outrageously expensive, you would pay about 30 Euros for 10 days of antibiotics for a medium sized dog.
so this is really payable. also, often the vet will take down-payments.
The longer you wait to seek veterinary care, the sicker your dog will get and the treatment more expensive. Cut away the hair around the abscess to get a better look at it. Perhaps the visual will impress your family on the absolute necessity of vet care. Abscesses are serious and potentially deadly if left untreated.
Oh gosh it is badly infected and it is an abscess,it will get bigger and bigger.Your vet should have a payment plan.If no go at all can you get hold of any antibiotics anywhere ??? to fight infection.Inn the meantime fill a clean bucket filled with hot water and two large tablespoons of salt well dissolved get a clean hand towel and immerse in the bucket then gently squeeze out and making sure its not too hot place it on your dogs abscess until it cools down then repeat this should bring it too a head and hopefully release the pus inside, never squeeze the abscess.
This is not advised if you can get to a VET, it can be risky .The antibiotics are important too...... you cannot leave him like this !!!something has to be done.You need to find someone who knows what they are doing first so they can help...... like a nurse.
Let us know how you go please.