[wtwo3]

Depending on the options you select, it likely won't take 3 months. More like 1.5-2 months, but it can definitely vary based on a number of factors.

The only things I can think of are long term rentals. You'll typically get discounted rates for month by month rentals from any of the major rental companies. You could also check Turo for a cheap rental (i.e. Toyota Corolla/Honda Civic) as they often times give steep discounts for longer rentals (up to 30% in some cases).

Another idea - buy a cheap beater car and then sell it once you get delivery of your BMW. It might be a bit of a hassle, but if you play your cards right, that could be your cheapest option (and possibly even be able to break even).