Unfortunately, levelling a crafting class while you're still on your way to 50 is painful precisely because of the lack of income. Later it's not hard to establish a steady flow of income, but in the meantime it can get very draining.

Levelling yourself a gathering class can help immensely, of course. Other shortcuts that can help include knowing what materials you can get from NPCs (some things can be bought from very specific locations - and only specific locations!), using crafting levequests to maximize your experience-per-craft (and get some rewards back), etc.

If it's becoming too expensive, feel free to back off of it for a while.