While I agree with all of the above comments to a certain degree, sometimes a large tank just isn't practical.
It has been mentioned that you should get a 55g and put around 25lbs of rock in, adding to that over the coming months - I would disagree with that as you would be better off filling a small tank with live rock than half filling a large tank and having to wait months on end before stocking it. Yes, a larger tank than a 10g would be preferable but I see no reason why you shouldn't stay 'Nano', ie. under 30g.
Upgrading from a Nano to a mini reef is not that difficult, the main expense being the upgraded lighting, as you would be following the same principal as mentioned by Dawhits. Move everything over and add to the live rock volume over time. The live rock you already have is enough to support your livestock already so as long as you don't add more bioload before you get more live rock you'll be fine.
When I upgraded from my 55g to a 120g all I did was transfer eveything over, admittedly it was a little easier as both tanks were 4 foot long so the lights moved over too, and then added live rock and bought a halide.
With the situation that you are in the cost of stocking a large tank may be too much whereas a Nano would be achieveable. You're not going to have the best equipment or the best setup but you will have something that you can afford. It is better to run a small tank affordably than to run a large tank and constantly be trying to find money, possibly to the detriment of your tank. I have heard of people who couldn't afford to buy food so their tank starved for a week, couldn't afford a new tubes for the lighting so their corals started to die, couldn't afford RO to do a water change so used tap water instead (without de-chlor as they couldn't afford it)........the list is endless
Marine tanks are expensive, not just in setup but running costs too. Smaller tank = smaller running costs which is why there's been an explosion in Nano tanks, especially for the younger generation. With the advances in technology and science it is easier than ever to keep smaller tanks and as long as they are researched properly and looked after they make stunning aquariums.
I personally would rather see you 3 months down the line with a lovely 20g Nano filled with inverts, corals and fish which is being cared for and looking good, than see you with a 55g half full and struggling to afford the stuff you need to make it look stunning