Hello,
Keep in mind that every domain that is still available usually is for a reason. Nobody would buy it for $10. Of course, it is an oversimplification but you should not expect to make a lot of money on handregs anyway. But when you're starting out, it's your best bet. Do a lot of research first, then buy a few, with restraint. Do not pile up a lot of domains until you've made a few sales and understand the market well enough.
Sales are the exception, thus domaining is much more difficult than it sounds. There is a bit of luck and timing involved, but it all boils down to the quality of your inventory.
Most of the great domains were registered long ago. If you want to build a quality portfolio, you'll have at some point to turn to the aftermarket and buy from current registrants.
Good luck.