Yup! LDD and the other digital Lego designers are really fun to play with. My ONLY problem with them is that the virtual building and designing lacks that tactile joy that Lego brings. But it definitely is easier to work with for budget and unsorted collection reasons!
And regarding designing/reselling:
Brickarms - these guys do custom weapons/accessories for minifigs. There's nothing wrong with this, either. They've been around for quite some time.
Brickmania - another site similar to Brickarms, these guys design and sell their own sets. The thing is, they're all VERY expensive. Think about it...Not only do you try and make up the design time in the cost, but you have to get people to pay for the pieces that you either parted out or bought from Bricklink (which can get expensive for tougher to find pieces). Add in a little bit of profit...
Take a look at this:
Pagoda. It's a cool set, but at just over 1500 pieces and costing nearly the same as the SSD...I say "Yikes". But it CAN be done!
Enjoy the new hobby!