Which airlines allow you to gain hours with them by paying them
There are pay to fly services, however regulations require a minimum number of hours before you can do any kind of part 121 or part 135 work. So while you can get some extra hours in Jets by paying them that way or turbo props or whatever else you’re looking for, it’s not recommended. Probably the best starting gate once you have a commercial pilot certificate is just doing flight instruction work until you gain the required 1500 hours.  After that you should have offers for most of the regional carriers to work for them as a first officer.