For a six mile round trip I would suggest going on line and looking at Citizen folding bikes.I own a Citizen Maimi I ordered for 199+30 dollars shipping anywhere in the US.I also own a Brompton folder H model priced at $1850,so I have examples at both ends of the spectrum.The Citizen is a very good bike for the price,good range of gearing(6spd) for any hills,20" tires,all steel rugged construction(30lb) and rides very well.I use it alot and if you get the rear rack it will carry a ton if stuff.An extra point is that it folds and can be taken inside just about anywhere, the office,walmart,the movies,coffee shops,supermarkets,etc.The 30lbs is not something you want to carry with you,the trick is to roll it just like a shopping cart or baby buggy and fortunatly the Citizen is one of the easiest to roll once folded up.You just leave the handle bars up right and they become the handle you push along.
And if you want something cheaper look at the 16 inch wheeled Tokyo for only $169.