What is the statistical likelihood of getting a job as a theoretical physicist? I'm considering taking a hobby (taking math and physics classes, reading attempting to read arXiv papers) and turning it into a career change. However, I have 3 kids and a wife who doesn't make a lot of money so I have no choice but to look at grim reality.
I'm willing to work hard, network with people, do research, etc. so let's leave effort aside.
What is the statistical likelihood of getting a job as an actual theoretical physicist?
 A: As an experimental physicist, I'm not perfectly placed to answer. However, the only job as a theoretical physicist, that is, doing theoretical physics, at least as far as I'm aware, is in a research/invited/appointed post at a university, special institution (Institute for Advanced Study, etc.), or (maybe) a national lab.
That said, there are more Ph.D. students coming out of physics than there are university positions for them to occupy. For a short version of why it's unlikely to get a job as a theoretical physicist, take a look at the Many Applicants, Few Academic Posts on page two of this article: http://www.scientificamerican.com/article.cfm?id=does-the-us-produce-too-m&page=2 (the rest of the article is worth a read as well).
The outcome of the situation is that a lot of physicists go into industry or other fields. But, industry doesn't use theoretical physicists as theoretical physicists. They use them in Wall Street for solving complex equations, for example, but not for physics.
I'd add to this that the competition in theoretical physics is rather significant, since it takes quite a special brain and a lot of training to make real headway on the deepest problems of the universe.
So, unfortunately, I'd say that the likelihood of getting a job doing theoretical physics is rather slight. And, given your economic constraints, it's unlikely you could afford to go through the low-pay period of a Ph.D. (a requirement) and a post-doc (in practice, also a requirement) in order to get an appointment in the field. If, on the other hand, you want to learn theoretical physics, even get a degree in the field, and then use that knowledge elsewhere (Ph.D. only), you might be able to swing that.
A: This is general information, since I really know rather little about you or your circumstances, but here it is anyway.
Talking about probability in relation to getting a job is not really the right way to approach things, in my view. What you need is a lot of dedication, a certain amount of god-given talent, and a real passion. Perhaps that understates it, even.
In terms of practicality, you'll definitely need to start by getting a Bachelors or Masters in physics (4 years), after which you'll want to enter a PhD programme, write and defend your dissertation (~3 years), get a job as a post-doc for a few years, and finally become a researching theoretical physicist. The whole process can easily take up to 10 years, so it's nothing to be done lightly! And at the end of the day, there's nothing to guarantee you'll be successful; it's a highly competitive field. (They also say it's one for the young.)
This is, of course, the route you need to take these days if you want to enter academia/professional physics. There is nothing stopping you from pursuing all this yourself, using the relevant resources, and publishing papers yourself to gain reputation. IF the other way is harder, this is even harder. (Even the greatest minds in theoretical physics needed some amount of education in order to grow.)
So in theory, there is nothing stopping you, but it's a very difficult path you're taking, especially if you did not begin it after high school. If you want any more specifics, I suggest you elaborate on your situation.
A: Stephen, 
I am sure everything you are reading here is horribly depressing, but unfortuntely true.  Barring vast personal wealth, the normal path to practicing physics is largely for the young and single.  However, that said, there is nothing that would be better than to get a good education in a more accessible field, and bring a passion for math and physics to it.  I would recommend taking math and physics courses, even if they don't lead to a career of a physicist.  You will find that because people with a passion for math and physics is extremely rare, anyone who has skill and determination can bring a considerable amount of illumination to their field.  
Now, the question of what kind of math to learn on short notice is important, and my answer to that is statistics.  I would also spend time learning computer programming, nothing complex, but maybe some visual basic in order to create macros in excel.  If you understand those two things and can do it well, you have automatically positioned yourself ahead of 98% of the population.  
Hope that helps.
