So, I thought about this a while. This is my only advice to any new aquarium keeper. After you have purchased all of your equipment and at the point you think you are ready to invest in fish, perform the following. Regardless of your income (and trust me it doesn't matter - if you can afford a $10 fish each week you'll spend $20 and if you can afford a $50 fish you'll spend $100) collect all of the money you have at the end of week. Out of this money, take $10 and put it aside. With the remaining money, flush it down the toilet. Spend the $10 on a Saturday night dinner. Repeat this process for a year. At the end of a year you will have managed to imitate what it's like to own a basic tank. If this feels comfortable, then by all means purchase a tank. Good luck with a small tank. From my experience a smaller tank (less than 55 gallons) is actually quite troublesome due to the temperature and salinity fluctuations. I have found that a 30 gallon tank requires a chiller to avoid expensive losses. For a bigger tank you will need larger pumps, more sand and live rock, more lighting, etc.
I will not continue to feed the troll. This is just the advice I give to all of my friends and family when they see my tank and ask how easy it is to maintain. I'm quite happy with my tank now and seem to have found a great balance (for now) but I understand that this will likely change. I've considered taking the whole setup down on numerous occasions due to cost, algae, power failures, etc., but I'm committed to making this work. If you can commit to this level then I wish you the best.
jim