Never a guarantee it will work out, but there are definitely opportunities to make some money during the summer. (Many people also choose to be a potato during the summer, which if that saves your sanity, go for it!)
Here's some examples from my own experience of summer job opportunities:
The summer before vet school I worked for the federal government and was paid well ($21/hr in DC). The federal government will pay you generally as a GS-7. Some GS-9 positions are possible too depending on the position and the level of education you have.
VMCVM has funded research opportunities at the school during the summer - students who do that get about a $5K stipend, I think, and don't have to worry about moving elsewhere for the summer if they want to stay in Blacksburg. No idea what other schools have going for them, but I'm sure at least some of them have similar research opportunities.
Lots of my classmates are sticking around Blacksburg and working at the school teaching hospital or at local clinics over the summer; some with full time hours if they could find it, some with more relief style hours. There are more opportunities if you're willing to work during the school year too - several of my classmates work for the teaching hospital at the school and are required to stay here during the summer to hold that job. There are also more clinic opportunities if you're willing to commute outside of the immediate area, especially at emergency clinics. If you go to school in a more populated area, in theory there will be more clinics to apply to.
Both Banfield and VetCor clinic have summer opportunities geared toward vet students. (Banfield has national reach; VetCor isn't nation wide, but has over 300 practices in many states). Banfield is more standardized because of the way the company is set up, I think, and pays what I consider a living wage based on what I've seen. The VetCor clinic wages are more dependent on the clinics themselves, I think, because their structure isn't set up the same way. It seems like they offer about what they would pay their vet assistants.
A few nearby humane societies have also been looking for seasonal summer hires here; if I hadn't gotten a clinic job for the summer I probably would have applied to them so I could stay at home. Pay isn't great at humane societies, but the hours are a little more consistent imo and there's an understanding that it's a seasonal job so you aren't expected to stick around once school starts again.
Based on my experience and my classmates experience, I think you should definitely be able to at least break even for living expenses during the summer. Depending on the type of job and location, you should be able to bank some money too if you are working full time and keeping your living expenses as low as possible.
