Epilepsy is common and usually easily managed. There can be complicated cases, but most dogs can be adequately stabilised and return to a perfectly normal life, even work. This is quite a lot know about it - much of the information carried over from people.
The medication isn't expensive. A 25kg dog would start treatment maybe one tablet twice daily and that is well under 50p/day. Yes there may be bloods needed to rule other things out, and occasionally to check the adequacy of the dose, but you should budget for vet costs or have pet insurance. Epilepsy is not one of the expensive diseases to manage, unless you are very unlucky and end up on some human medication!
Assuming the dog is young then idiopathic epilepsy most common, it's often bad news when an older dog has seizures.
Occasional seizures are ok so long as the dog recovers quickly. Even when treating you will get some. What we don't want to happen is leave the dog untreated and it will keep having more and more seizures. My simplistic explanation is driving - it takes a lot of mental effort the first time you drive a car, but the more you drive the easier it is and the less of your conscious brain is required - same with the fits. Each fit makes it a little bit easier for another one to happen. You need to keep a diary. Your vet may prescribe something you can have at home to help bring the dog out of a fit, but that is between you and them.
Good luck.