How would you start up a vegetarian drive-thru/dine-in?!

You need to answer a few questions to see if it is doable.
1. Is there a customer base to support it? A lot of vegans in the area?
2. Reliable source for quality product?
3. A good variety of recipes?
4. Cost of owning/renting restaurant
5. What will people pay? What do you need to charge?

Good luck.

You get a quarter of a million dollars or so together, maybe more depending where you are, do some market research to find where's a place you're likely to get enough customers, find a place to buy or lease where you're allowed to have a drive-thru restaurant, get all your permits, design the menu, hire the staff, go for it and hope you make money. Same as starting any kind of restaurant. Restaurants have about the highest new business failure rate there is.

The easiest thing to do may be to do something ethnic from a county that has a lot of vegetarian foods like India. Just delete the meat products from the menu.
To Cliff. Maybe you should get some reputable sources. Many truly reputable groups such as the American Dietetic association disagrees with you.

I agree with Keith on his questioning...

But I suggest googling recipes for making a vegan patty (or buying some... you might need permission from them company first!) and get some buns (maybe whole wheat for health?), make some tofu dishes like miso soup or tofu grilled and sauced, make some really yummy salads (get creative!).

Things like that... but to get a whole building to even think about starting a vegan drive thru, best be checkin' you have money for it! Or else it'll kind of just all fall down on you...

Good luck! This is a great idea!

I would be honest with my customers. I would offer meat-based and vegetarian options and distribute literature warning my customers of the potential dangers of vegan diets:
http://www.listen2yourgut.com/blog/dange…
http://chetday.com/vegandietdangers.htm