EDITED TO ADD some info:
I do not know about what guinea pigs can catch from rabbits — There are a few members here that may have better experience with that, who I hope will answer.
I know vet care can be expensive, and your bunny is just fine right now behavior wise, but if the infection, tooth problem or another issue is allowed to worsen, you could end up dealing with an emergency –being prey animals, rabbits are great at hiding illness. They usually won’t show something is really wrong until it is actually life threatening. And when that does happen, it can take less than 24 hours for it to turn critical, and emergency care to help save a bunny can really be expensive. I’m not trying to scare you but caution you about relying on his current behavior as a sign of okay health. He is exhibiting symptoms though that show something health wise physically is not right. I know you said you would be taking him to a vet soon, and you are looking to find the right one. I just don’t want you to wait tooo long.
For things that come up that are over my budget, I have been aided by a couple of things. I have a Carecredit Card – it’s a card that can only be used for health care and vet care. (And it offers 3 month, 6 month and 12 month deferred interest plans). Not all vets take carecredit — so you’d have to make sure yours does before you apply for the card in the first place.
A credit card can come in handy for this kind of thing as well. I know it’s not ideal because you have to pay extra in interest, but at least you are not stuck in a situation that could get worse both emotionally and financially.
I have been able to work out payment arrangements with my vet. Of course, my current vet knows me and I’ve been seeing for awhile, but one time we had to take our cat in for emergency surgery, and it was well over $1,000! This is a vet I had never been to before and they allowed us to make payments. They didn’t even do a credit check. So it doesn’t hurt to ask. So you can get an appointment, find out what’s wrong and if it ends up being over your budget for some sort of ongoing treatment, then discuss payment plan options. If within the appointment you find out it may be something that needs to be treated soon (tooth issues), but isn’t urgent at the moment, you would at least know what needs to be done and what you need to start saving for.
When I was much younger, I was able to get a loan from my folks, which I paid back, so I don’t know if you have family members that would be able to give you a loan if it got over your budget.
And, you might find it’s just an infection that can be fixed up with a couple of weeks worth of antibiotics.
I know it’s a very difficult situation to be in with finances being limited. Believe me I do get that. We have seen some tough times ourselves. Which is partly why after my bunny and cat passed away, we chose to only have a single bunny for now — until we can build back a decent savings for vet care– the last vet savings had been wiped out from tooth issues, cancer, E.C from previous animal health issues over the years. And my current bunny is a senior and I am preparing for the financial things that come with that — so far knock on wood, she is doing great. But just from my own experience, it is really rare that within your animal’s lifetime that you will only spend $200 for just one animal, and you have two bunnies, so if there is any way you can begin saving a bit more over time, it will help with the care your animals may need and it may certainly offer you more peace of mind.