If I were to start my own fast food business, I would make my food cheap as fuck and deliberately target locations that have:
A sixth form or university campus nearby. Students are a big market.
Nearby pubs or nightclubs. Doesn't have to be a city centre, could be a local high street. The main intent would be to target the late night crowd.
People care about speed, cost and not eating something that will give them food poisoning, not gourmet food. The luxury market is oversaturated and we have anything but the luxury to do that often.
Also, if it's a sufficiently large eat-in location like a diner, maintaining toilet facilities that don't look like they've been vandalized is important too.
I agree, there are still ways to sell your food cheap though. A good example is a vegan/vegetarian burger place near me. Demand for that kind of food is high because it's a liberal college town, but that restaurant is the only one of its kind here, so it's always full. Also they sell more fancy, more expensive dinner options in the evening which I'm sure subsidizes the cheap burgers. And if you mainly go there for their burgers you might return for dinner sometime to try out those options. They've existed for around 10 years now and their cheapest burger has stayed at 4,50€ that whole time.
Granted it's hard to know what kind of demand there is in your town without trying some stuff and maybe failing.
They usually aren't happy when I take a shit inside our local food trucks. They keep telling me it's unsanitary but I always insist that a restaurant must allow its patrons fair use of their toilet facilities.
The most popular pizza place near campus had only enough interior seating for a couple people waiting for orders. They stayed open until like 2am and the late night crowd loved them for it. They definitely capitalized on drunk college kids with unusual flavors like Mac and cheese, or mashed potato pizzas.
I hate how this society has turned something as deeply emotional as cooking and turned it into a factory farm where people think burgers and hot dogs just magically appear with fairy magic.
Check out how successful Dick’s is in Washington. They have so many locations now. Their first location was Wallingford, Seattle. It’s about a 1 mile walk from the U district, where a lot of the college kids hang out. Now, Dick’s has a location in most major districts of Seattle, mostly around bars, and even outside of Seattle. They are cheap ($2.50 for a cheeseburger) and super fast because they don’t do customizations with a limited menu. Mostly window only walk up pick up, no dine in (except for the one outside the hockey stadium, but it’s standing only).