I'm really tempted to invest in one and have some questions

Unless you have experience setting up and keeping a freshwater tank - I would hold off or go freshwater first. Get the biggest tank you can afford though... I got my 125 gallon freshwater setup for around $1200. The filter alone was around $250 or so - I recommend Eheim filters.

Find a store near you and talk to some people. Also, you can find some good deals for stuff at big als online

The fish are (usually) the cheapest part. Its tons of fun and worth the effort!