My philosophy is NEVER pay interest unless you can deduct it from your taxes or you need it to establish credit, then pay off the loan.
I just bought a very nice, very slightly used BC on eBay for $18. It's a Dacor so most people won't buy it because parts aren't available. However, just about any part that might fail can be replaced with standard parts. I bought a very good used Sherwood second stage for around $30. I bought a very good used Sherwood first stage for around $25. I now have an extra, very good regulator for $55. Hoses and gauges and such things just sorta happen over time. I bought a brand new full 2.5mm wetsuit on eBay for $30 (including shipping). It fits great and I love it. I bought two pair of genuine ScubaPro Jet Fins on eBay for $60 total. They needed new straps. I love these fins. My girlfriend bought a pair of Medium ScubaPro jet fins at the second-hand beach store on Hawai'i for $20. They needed new straps too. She loves them. She recently bought a new 3mm wetsuit from Scuba.com which was on sale for $65 instead of $120. It's a very nice suit and it fits her great. I made my weight belts from fishing weights that I found while diving. I think a buddy gave me the mold.
Hang around some people who have been diving a long time and they most likely will have extra stuff that they don't need or you can at least try out before spending a lot of money on something you might not be sure about.