ATV0121:
Certainly there are other things I'd consider doing - journalism, press secretary of some sort, work at a publishing house, maybe PR or advertising for the right company - but none of these comes close to appealing to me like just being a stay at home person (eventually dad) and writing books would.
Okay, this is going to sound a little harsh and negative but I'm only saying this to try and give you a sense of perspective about this.
You currently have 3 novels in various stages of production. You don't say how close you are to having any of those in a state ready to go out on submission to agents, so I'll make a conservative estimate and assume you're about a year away from having something ready to go out.
On that basis, you start querying in May 2010. You could hit the jackpot on your first attempt and secure the agent of your dreams. Alternatively, you could be stuck on the query, partial, full rinse and repeat cycle for anything up to a year/18 months before you get an offer of representation. You could even get to the end of your query list and not have secured an agent, in which case you'll have to start again with your next book.
But let's be conservative here, say that after 12 months of querying you get an agent. That takes us to May 2011.
Now your agent loves your manuscript but has some notes on changes that have to be made before they're prepared to send it out to editors. It takes you, say, 2 months to make those changes and get a manuscript in a shape that the agent is happy to submit.
We're now in July 2011.
The manuscript goes out to a bunch of editors. A couple make encouraging noises, some of them auto-reject it for whatever reason (not right for their lists, they've already got a similar concept etc etc). Unfortunately, no one making encouraging noises loves it enough for your agent to decide that it would be worthwhile putting it to auction. So instead you wait for each of those editors to run it past their marketing bods and editorial boards. This takes, say, another 6 months.
You're now in January 2012.
One of the editors has decided to buy your manuscript. Your agent then begins the negotiation process for the advance and other contractual issues. Depending on your bargaining position and how skilled and efficient your agent is, that could take another 3 months.
We're now in April 2012. Up until this point, you have not received a penny for your manuscript.
However, once you have your contract signed and dotted, the publisher pays the first part of your advance. You're a first time author so you got the average going advance for a debut work - $10,000. The advance is split in 2 - half on signature of the contract, half on delivery and acceptance of the manuscript. Therefore, as at April 2012, you will have $5,000. For 3 years work. And you'll lose 15% of that $5,000 to your agent as their fee.
So for 3 years work, you have actually received the grand sum of $3,750.
It takes another 9 months of going backwards and forwards with your editor before you get to submitting your final manuscript. That takes you to January 2013, at which point you get your remaining advance of $3,750.
In the summer of 2013, your book is released into the market place. It could be a massive hit straight off the bat. More likely however is that you'll do reasonably well and end up midlist. Depending on the terms of your contract, you won't start earning royalties unless and until the second or third print run. That could take you to the end of 2013. Those royalties will be a welcome amount of cash, but unless you've had a good seller, you shouldn't expect to receive more than another $10,000 in total (and remember that this will be payable quarterly and calculated as against returns).
The point I'm making is that 4 years can go by and you won't receive a massive amount of money for your hard work (and I haven't even begun to factor in the tax payable on the other example sums, or the amount you'll need to pay in health insurance and what you'll lose in other bills).
Now, it's possible that you'll end up publishing several books a year or you could hit paydirt with your first novel and make a mint but you shouldn't count on that happening. The figure that gets bandied about a lot is that only a v. small percentage of writers actually make a living from their writing. An awful lot of writers find themselves having to take on another job to supplement their writing.
The best advice that I got from a professional writer was to marry someone rich and willing to support me (but the economy is really wiping out all the single Russian oligarchs who I'd normally consider

), or to make sure that I've got a decent job behind me that will pay my bills while I'm waiting for the writing to start paying off.
Personally, given that you're at college I think you need to work out now what job you want to do on a 9-5 basis that will support you while you're writing without interfering with the writing process. If you've got a good profession behind you that will always enable you to find work then that's invaluable because it will help you to stay on your own two feet. Once you do start to make the big time and you've reached the point where you're writing is earning enough to support yourself and your family, then you can consider packing in the job.
Hope that's of some use (and again, apologies for the above sounding harsh).
MM