I would just like to say that passion does not always translate to money. Some interests remain as avocation. However, if it is something that you really enjoy doing, then my advice is that passion will push you through the hardship. Otherwise, if you are good at something that makes you money, money will push you through even though you may not like it.
For acting, you can search online for auditions. There are many online auditions globally today and remember to start small, and take things step by step. Also, you can use youtube tutorials to hone your acting skills. That way, your passion may turn into money.
Now, there is a saying that says "all roads lead to Rome" meaning you have many avenues to get to your goal. If you need a side job to get some money while you work on becoming an actor, do it. I believe that is how many of today's actors began their acting careers. Any, any job you take will always add to your personal and professional development, any job. All the experiences will add up to make you a better person and professional.
Great question! It is an eternal dilemma. There are several options here.
Option A: Save up about 6 months-1 year of living expenses and pursue your dream of being an actor 100% without a backup plan. Put yourself in an area where there are a ton of opportunities, audition every day, take acting classes, etc. Basically, go forth and try to make it. This has worked very well for many of my friends. Tom Cruise's parents apparently gave him 7 years of paid living expenses to try and "make it," and we know how that turned out! Obviously, if you can stay with someone rent-free for a while, that certainly helps too.
Option B: Get a B.A. degree in Theater (which can help springboard you into tons of other jobs upon graduation if you decide that theater isn't for you). Audition for summer musicals and plays or teach summer drama camps in the meantime until you graduate. Attend SETCs and audition every year--try to get acting gigs, traveling wherever the work is. Many companies will provide housing and a weekly salary while you are under contract, you just need to stay mobile. Either continue to pursue theater 100% or get an office job working at a theater and then perform in plays on nights and weekends. A very busy schedule but certainly doable! Pay your bills AND work professionally in theater. I will say that a degree in theater doesn't necessarily guarantee that you will work in theater, it just gives you the skills to be successful if you put the work and commitment in. **On a side note: being a freelance headshot photographer actually works really well with being an actor on the off-chance that you have those skills too**
Option C: Major in something else that is more guaranteed to make an income and either minor in theater or just pursue acting as a hobby. There's no reason that you should have to make money being an actor and only do that for the rest of your life. Some folks are perfectly happy doing theater for fun and not worrying about it sustaining them financially. It's sometimes better this way because being an actor is super stressful. It's really hard to have stability.
I hope this helps! Good luck in your artistic pursuits!