Not gonna be cheap, buddy. Youre looking at at least $600 in lights, $200+ for a good in-sump skimmer, probably $100+ on a diy sump, more if you buy one made. Plus $100+ on plumbing, another $50+ on a return pump. You also need powerheads, probably $150+ for those, heaters are gonna bee another cost. Youre looking at $2000+ and then tank, stand, salt, rock (which youd need at least 260 lbs) and sand. After its set up, you have livestock and corals.
Point being, it isnt a cheap hobby by any means, but its a great one. If you choose to pursue, youve picked a great site to join, everyone is really helpful and someone will be able to help you every step of the way. Remember to go slow, its not a race (think of the tortoise and the hare).
Post any questions as you have them and good luck!