On one hand, you could search this forum with the keyword - Paris and many hits will turn up. Use the search box/button at the top of this page.
On the other hand, Paris is riddled with affordable (cheap) eateries. Wander around and look into the various places. The good ones are usually busy and not just hosting a bus load of Chinese tourists.
If the place is full of local residents....even better! The more colourful and cheaper (student haunts) areas are Marais, Latin Quarter, and off, off St Germain de Pres.
An option is the N.African enclave in the Latin Quarter with cheap food from Maroc (Morocco), Algeria, Tunisia in the form of tajine stews with cous cous. The cous cous is free flow but you have to pay for extra stew. Seating may be along benches in a communal style.