There are agencies that act as intermediary for healthcare workers to pick up travel gigs. You sign up with the agency. Hospitals/laboratories/etc who need short term staffing solutions (laughs then sobs in COVID staffing shortage) reach out to agencies saying they need a nurse/medical assistant/medical laboratory scientist and the agency sends them the resumes of all their contract workers that are available. If the facility wants you, the agency contacts you to see if you want to take it.
Housing/living expenses are covered and you make BANK compared to the permanent employees (who may resent you for it). The travel pay and contracts are slowly returning to pre COVID levels but it was ludicrous for a while there. I did try to figure out a way to take a leave of absence from my job (don't want to lose that pension) so that I could pick up a travel gig. It was that lucrative. There's always a staff shortage in healthcare somewhere in the country.
There is potential for feast and famine so people doing it as their sole income need to plan for that or be willing to work in facilities that are a dumpster fire or in places that they wouldn't relocate to for permanent work. Most contract agencies don't offer benefits so that also needs to be planned for. Travelers usually make 2-3 times more per hour than permanent staff and have a separate allowance for living expenses so getting your own health insurance won't negate your earnings.