There are those who mattir teaching in a conservative synagogue, but it’s definitely something discouraged even by the mattirim. I assume nobody would tell you to get a job there to pay tuition.
But yes, plenty of people to cheat the tuition committees, which is why they have become so mch more invasive now. One of my rabbeim mentioned that in a certain school, someone came in to the tuition meeting driving a jalopy and listing his address as a run-down building. turns out he owned the building in question, and borrowed the car from his janitor. When confronted, he paid the full tuition, and later gave the school a large donation.
Yeshivas are a necessity. They definitely come before paying for kollel.