First, don't ever ever ever expect to make a lot of money with engineering. Its one mighty gold-sink.
Second, im not an engineer but i do suspect that scopes sell for quite a bit. Bullets too, perhaps.
Third, if you have picked up engineering, you would also have picked up mining. Now, mining is one mighty gold-maker so make full use of it. Every ore sells, even copper.
Fourth, to be able to have money, you can not spend any money at all. Enough said.
Fifth, what alot of people like to do is to pick up 2 gathering professions (mining, herbalism, skinning or disenchanting), make alot of money while leveling to 70, then switch and powerlevel a new profession. Saves any worries of money shortages and headaches of leveling your craft.
Cheers.