If your just going to sell it at the end of summer and your commute is less than two miles any bike will really do. You don't necessarily need to buy a bike from a bike store. A department store bike or a cheap used bike off Craigslist, less than 100$, will suit your needs. Your going to take a hit on the new bike price wise if you try to sell it. The lower end bikes are not necessarily that desirable for resale unless they are a lot cheaper than new, but you might get lucky.
I commuted round 5 months 20 mile round trip on a department store bike before I bought my Trek and that was manageable, so two miles one way on a cheap bike would be nothing.

But if your planning on keeping a bike and continue commuting longer than summer, which would be a wise thing to do, then you better off spending closer to the 500$ mark for a good entry bike.