I'd have to agree, for the most part, with the estimates of others posted so far but don't be discouraged. Start out slow, maybe just a BP&W, you need that to carry the doubles. Then maybe a set of AL doubles and another reg so you'll have a set. You can always dive mixed gear to start. Dive with this gear for awhile until you can afford to add something else like a deco bottle and another reg. I started out this way because I couldn't afford to buy all the gear at once either. I dived the gear recreationally for about a year before I had saved enough money for the first class.
If you know what you want you can find some really good deals on Ebay. I got my AL backplate with harness, new for around $50 and my latest set of new Apex DS4/xtx regs all set up for tech diving with 7 foot hose for $650 for both. I've bought a lot of used gear on Ebay as well. I had one AL tank to start with and bought a second for $50 plus shipping and a set of bands for them for $30. You just need to know exactly what you want and ask questions to make sure it's in good condition.
If you know what you want you can find some really good deals on Ebay. I got my AL backplate with harness, new for around $50 and my latest set of new Apex DS4/xtx regs all set up for tech diving with 7 foot hose for $650 for both. I've bought a lot of used gear on Ebay as well. I had one AL tank to start with and bought a second for $50 plus shipping and a set of bands for them for $30. You just need to know exactly what you want and ask questions to make sure it's in good condition.