Don't do it lol thats all I can advise you. Honestly rentals in Boston are far more expensive then Orlando. Most rental agencies will drive to you pick you up take you to there office to fill out paper work and then you on your way. Thats one option, many hotels have a rental office located in their building or you could take the mbta to a rental office. Whatever you do don't try to just get a deal walking up get your deal before you get here and don't tell anyone but call and see what rates they have. I don't know why but I've gotten really good rental rates locally just by calling. Usually to get a van to go on a serious roadtrip with friends but still I've gotten better rates then quoted online.