It depends on where you go. Keep your eyes open and update regularly once you meet an airline's minimums (usually around 1200tt and 200-300 multi). Also, work on networking. CommutAir, for example, recently hired a number of instructors with <1200 tt. They did almost universally, however, have recommendations from current pilots with the company.
Also, if you limit yourself to flying for the regionals, it could be a very long wait. Look into other options, once you meet 135 IFR PIC mins, start applying to the freight operators, charter companies, etc.. 1-2 years of instructing should get you those mins. Planning is important. Keep in mind the industry is very dynamic. Keep a close eye on the hiring trends. Apply early, apply often. Flexibility is key, if you are able to relocate, many more doors will open for you.