I was about to say, don't start up your own business until you have a lot of experience working with other people's dogs in a professional setting--sounds like you already know that, and are planning to work as a vet tech to gain that experience. So far, you're going down the right path!
First and foremost, you have to get used to the idea that, unless you have GOOD, trustworthy staff, you can never take holidays off and you can't call in sick. Vacations must be planned months in advance; no last-minute trips to the mountains or the beach when you own this type of business. If business is good, and there is always demand, you'll find it very difficult to even take one day of the week off. It's kind of like being a mother, it's a 24/7 job.
I do grooming for a living, but I will also board my clients' dogs. It's not something I advertise, it's just a convenience I extend to clients only, as I do not have a kennel license. Just with the very limited amount of boarding I do, I've found that major holidays are always the busiest times, so if you want to have a nice Christmas visiting the family, forget it.
For me, the hardest thing about boarding is dealing with liability issues. Even though I've never had anything bad happen, I always worry and imagine worst-case scenarios. You have to engineer in a lot of redundancy into your safety and security measures.