As you say, soprano is meant to be harder to play for a novice than an alto or tenor. I wouldn't discount the idea of a tenor, arguably marginally more useful to play popular (soul, discount, rock) music in a gigging band.
I wouldn't buy any brand new instrument unless you have the budget to buy a decent professional instrument. Unfortunately, there is no link between using the vendor using the word 'pro' in the description and it being any use. If you have the budget for a decent, new professional instrument, to me that would be Yanagisawa, Selmer, Yamaha (Yamaha's does usually genuinely describe it's professional level properly). Most other new instruments may never be good enough to learn on, play in tune and might never be good enough to gig with.
If it were me, I would buy the best second hand instrument you can afford but you will need advice. As a PP has said, the right/good vintage Conn, Buescher, SML, selmer, Martin will sound better than almost all new saxes. If you don't know a good player for advice then I would seek a good local tutor first and explain you want to buy an instrument if they don't have one to hire then seek their advice to buy a good second hand instrument. The other advantage of buying a good second hand instrument is that you probably would be able to sell it for about how much you paid unless you overpay.
I wouldn't use one of the rent to buy schemes for new instruments as these usually involve instruments that won't be good enough for you.
If you're already a guitar player then you'll be part way there already. I think it's harder to go from a single note instrument to a guitar/piano/playing in a band than the other way.
cafesax (If Pete Thomas? is still involved then he's a great chap in my experience) is a good forum as a PP has said. saxontheweb is one of the biggest and best.
Welcome to the world of mouthpieces, ligatures, reeds, microphones and everything that affects tone a little.
Good luck.