[tony20009]

I travel for business some 60% of the year. I just pick up whatever is in the aisle at National Car Rental's airport locations. They usually have a fair selection of typical cars. All are sufficient for functional transportation. Though I use National most often, you may find that other companies are cheaper, but Hertz and Avis won't be those companies.

In the DC/Baltimore area there are quite a few places from which you can rent pretty well anything you want. Enterprise Car Rental generally maintains a booth in most new car dealerships, and in most cases you can expect they will have available cars that correspond to the brand of dealership at which a given booth is installed.

Enterprise at the BMW dealer I use has half a dozen or so F30 328i cars. They may have other models. All the ones I've encountered are base cars and sparsely optioned. That said, I still prefer that to an Altima. If you specifically want a BMW, or MB or Audi, etc. you'll want to speak with the folks who work that specific booth and find out when one of their [insert the brand you want] brand cars will return and ask them to reserve it for you. The reason for needing to do that is because they (Enterprise) are typically in the dealership to support the dealer's need for overflow free loaners. So, that being the case, you'll likely have better luck getting something specific if the dealer you go to offers free loaner cars.

If you don't want to go with Enterprise, and still want a premium car that isn't available from one of the national rental companies, use Google. There are several companies in the area that rent premium cars, even Astons, Ferraris, Bentleys, etc.

All the best and good luck. Oh, and no, there is absolutely nothing economical about renting a 328 or something like it, unless by "economical," you mean, more cost effective than hiring a private driver or renting a Bentley. LOL

PS
I can't believe at your age you aren't keen to drive across the US. It takes about 6 days (if you aren't just outright hurrying). I would have jumped at the chance to do that when I was 18-21, but the opportunity never came. Ce la vie.