Not sure about the SV650 as a recommendation in this case. Great bike, it would definitely be on my list of possibles if I were looking for a new bike right now, but if total cost of ownership is a consideration, you REALLY have to keep the gas usage down to keep a motorcycle in the black, and I imagine those get about 50mpg? Not good enough, imo. Ninja 250 and Nighthawk 250 are good. Also there's a fairly new Honda CBR 250, if you can find a good deal on a used one, those have a really good power to gas mileage ratio. Coworker of mine just bought one as his first bike and I test rode it and then rode it home for him on the highway. I'd buy one in a heartbeat.
Suzuki also makes a couple 250cc bikes. I don't see them often, but I'd keep them on the radar.
As far as brands, stick to the big 3 (Honda, Kawasaki, Suzuki). I wish I could put Yamaha in there but they're really not a player in the small displacement motorcycle market. For working on your own bike, I lean towards Honda. Having worked on the others, Honda design tends to be a little less annoying to work on, but YMMV. If you go for something older (80s or 90s, I wouldn't go 70s do to reliability, unless you get two bikes so you have a backup), manufacturer parts availability seems to be more reliable from Honda.
There are also a gazillion scooter options that can be worth checking out if you can find a good deal on a used one. They are more rain-friendly, as they have floor boards to protect you a bit, and under seat storage for grocery runs.