Should I buy or lease?

Early on, lease or buy used. $25M does not buy a new narrowbody and an aeroplane sitting on the ramp earns nothing.

Leasing costs more over the life of the aircraft and much less today. Buying used is the middle path and what most openings should do.

New aircraft make sense once you have the cash to spare and a route that will keep them busy — they are cheaper per hour and they do not go into the hangar as often.