My first bit of advise would be to hire a qualified consultant that can help you with many of your questions. Rather it be our company or another. My reason for saying so is if you plan on having a successful business, stop beating around the bush and invest properly in the beginning. Sure you can always get others opinions on what you should do, however, investing in a good consultant can lead you in the right direction without a bunch of guess work. It's a great benefit to have someone working with you from the start to the opening. Additionally, you can also employ them to put on training that will be valuable to your business, as well as on going consulting throughout the life of your business.
As for the cost of equipping a sit down type of operation, and 900 sqft is going to be quite a bit more than the 50K you are looking to spend. Actually you can erect a drive thru for about that cost. But keep in mind that the overhead to run a sit down shop is at least double than that of a drive thru. A few examples would include, the rent, the furnishings, dishes, display areas, utilities, multiple coolers, more equipment, and more supplies. And we haven't even addressed the cost for architectual drawings and permits. Things can add up pretty quickly and they do. If you are going to do this business it's best to invest wisely, and not go into things half way.
Just my two cents for what it's worth... :wink: