Or seek out a used Yamaha Yas 25 or 275 - as long as it is in good condition, you will be able to sell it for what you paid for it when (if!) you upgrade or heaven forbid, give up. That's what I did - cost me £400 which is exactly what I sold it for (this was 10 years ago). Just make sure you don't pay over the odds and get someone who can play to check it works properly before you part with your cash. They last for ever as long as they are not abused.
I had a Jupiter 500, but I struggled with the mouthpiece - my teacher loaned me a selmer c* which made a phenomenal difference for me.
I traded the Jupiter in (for what I'd paid for it) when I bought my Yani 901 back in February.
I started with a jupiter 500, which is a cheaper option than a yamaha 275, then moved onto a yas-25 (which is a great sax). Depending on your budget, i would either go for a jupiter 500 or a yamaha 25 (good quality second hand is the best for both... you can get some great deals then sell them at the same price, or in my case, more!) I bought my jupiter for £250 brand new, played it for two years (actually put a dent in the bottom of it) then sold it second hand for £270! The same story for my yas-25, bought £600, played 6 years, sold £650!
But what really makes a difference is the mouthpiece. I would recommend starting with a selmer C* (probably second hand) which second hand should cost you about fifty quid.
Also, one youve been playing for a while, try out different brands and strengths of reeds. I have two mouthpieces (one plastic, one metal) and use a different reed strength and brand on both.
PS. don't be tempted by gear 4 music. I had to borrow a brand new one of their saxes when mine was in being serviced. Bleargh...
Sounds good, and anyone buying it would have a good chance of getting most, if not all, of the money back when they decided to upgrade.
On the mouthpieces, there are a few standard recommendatoins: Yamaha 4c, Rico Graftonite B5 that are good to learn on and give a good sound. There's a Runyon in another thread that Tom M is recommending as well. The Selmer's are very good, but quite a lot more expensive.
I would have to put a good word in for the Bauhaus Walstein Alto - generally around the £400/500 and possibly the best at under £1000. As Kev said the Yamaha/Rico Graftonite/Runyon 22 mouthpieces are all worth investing in at £30/£15/£30 respectively to get the best out of the saxophone, as are decent reeds/ligature etc. Also recommended are the new Windcraft saxes (Richard Hamer - university sax tutor/pro musician/woodwind repaairer has given them a glowing report.
If you want to spend a bit more then a good used Yanagisawa A901/Yamaha YAS 62/Selmer would be an excellent investment.
The Yamaha YAS275 is well balanced and an easy instrument to hold and blow for a beginner if you have the budget.. There are others ive tryed out for beginners like the jupiter 500 and 700 range, Selmer-conn have a desent well priced range like the AS710 or the Elkhart 100 all of which i recommend to students.
most importantly if you not buying new, get an experienced player to inspect it and try it for leaks etc.
www.jazzshed.co.uk have a used Yamaha 275 Alto and 275 Tenor at £500 and £575 respectively - excellent firm who repair their own instruments and also teach sax etc. based in Cheltenham. Still personally would go for a Bauhaus Walstein every time as you are unlikely to need to sell it ever IMHO, so trade in value is irrelevant. A similar issue used to apply to brass instruments produced by Brazilian firm Weril, whose instruments would always outshine Yami and Vincent Bach instruments at less than half the price (Flugelhorn, Cornet and Trombone particularly) but were not widely known.