It depends on where you live I guess. Where I am, there are about 10 companies in my area that hire EMT's so it shouldn't be that hard to find an entry level EMT job. 125 pounds with someone else, right? Not alone. That isn't hard with a partner.
With CNA, you will usually always be able to find work and since you only want to do it for a few years, maybe you should do that instead. I think the training for CNA is about the same amount of time though... and cost.
You surely will be as a CNA. The whole point of CNA is to do what the Nurses don't want to do and provide basic, daily care to people who can't do it for themselves... usually in Nursing Homes or the Hospital.
If I train as an EMT and pass everything, I will be making it my career. I think CNA is more of a short term kind of job.