If you're cheap then maybe this isn't the hobby for you.
jk. Lot's of things can be done inexpensively.
To answer your question, it all depends on what type of corals you want. I would think your current lighting is fine for just adding live rock. I had a buddy who had a 55 gallon with two 30 watt bulbs over it. He had some live rock and had an aptaisa or two sprout up and some grape algae. But that's about it. But the live rock didn't 'die' off.
imo, I would go ahead and shell out some money now and get a retrofit vho kit. You can find 4 48" bulb, 440 watt kits for around $130 I believe. That includes everything except the bulbs. That seems like a lot now but believe me, you'll be happy you have it if you get into this hobby and start to see cool corals you want to add to your tank. With 440 watts over a 60 you can have just about anything.
If you're a real diyer then get a workhorse ballast for around $40 and hook that up with a couple of vho bulbs. 220 watts of lighting for about $55 after you buy the endcaps and wire.
Also, a 48" vho bulb puts out 110 watts of light compared to a no 48" bulb which puts out only 40 watts. But I've found that they cost almost the same! Only a few dollars difference. I can get vho bulbs cheaper on the internet than no bulbs in local pet stores!
Remember this. It's cheaper to go ahead and get good lighting than buying corals and trying to keep them under poor lighting only to have them die. After which you'll probably upgrade to better lighting anyways.
