If you need to build time, there are a few regional airlines in the U.S. that are hiring fairly low time people.
Get your ATP minimums and get the rating. Since you started in business aviation, a brief fling with the airlines won't hurt your job chances when you go back to business aviation.
Paying for a seat is like being a prostitute--you may only do it once but you'll carry it with you the rest of your life.
Good luck.TC