By "decent" I imagine you mean something to give to venue owners, booking agents, etc., in order to get your more/better gigs.
My advice would be to save up for studio time. Recording to tape would be your first handicap, as it is infinitely easier to make higher quality copies of CDs.
Second, yes, there are some high quality home-recording units out there, but a real studio will give you much much more professional-sounding results.
My band recorded through our guitarist's girlfriend's dad's project studio. Nice gear from Sam Ash, decent set up, and unfortunately sounded like crap. Bare bones and effective? Yes. But what happens when you need compression? Or just the right amount of reverb? Or you need to take a little bit of 1k out of the guitar? There's a huge level in flexability that you lose in an all-in-one setup. A studio has a plethora of tools they collect over time to make the little differences that add up to a quality recording.
Our drummer's brother does live sound, and could record us to 2-in tape. He knows what he is doing, set it up, recorded us live, and, yep, it didn't turn out as well as we liked.
Instead, we went to a studio that very reasonably charged $35 an hour, did a series of four 2 hour sessions (with four band members it came out to less than $20 a session, so easily less than $100 each for the whole shebang), and came out with a demo we are proud to give to people. Three songs, some rushed but effective mixing time, and we were done.
We also got a break on mastering from a friend of ours, and if you can get that done for a reasonable amount of money, that will also raise the quality of the demo greatly. (Assuming you get someone who knows what they are doing.)
It ultimately comes down to how much money you want to spend, and what you want to do. Buying a $300 Tascam multitrack will not give you a high-quality digital demo, but you'll have something to play with, and something to own. The studio time is a one-shot, but, in my opinion, is a far better investment.
(Whew.)