Yep. Can survive on smaller planes in JA quite easily.
And as for not making enough to cover C-checks, there are some tricks to that, depending on what you're flying. The balance of maintenance cost vs lease cost can be VERY different to what it is in later worlds, with bigger planes. For instance the Curtis Commando typically costs about the same amount to C-check (or more, I forget) as it does to lease for 12 months. And there is a practically endless supply. Therefore you should NEVER actually c-check on of them yourself. Go to the market, lease whatever is cheapest, and 10+ months from c-check. 10 months time, lease another, and terminate the lease on the old one. Costs almost nothing, and no problems flying your fleet of 30+ Curtis planes while you wait for f27 or whatever you plan to fly longterm to arrive, without ever paying a cent for heavy maintenance.