i disagree with many people here suggesting you start out with a rebel. while it is a great camera, if what you want is a camera to learn on and grow into, i think the controls on the 30 or 5 are better for learning photography, frankly. and there is no real virtue to 'starting at the bottom'--i think it is more important to start at the beginning, with the basics. the 30d and 5d are perfect for that.
i had a 20d, now a 5d. they are both excellent cameras, and they both have some shortcomings (mainly in terms of auto metering and some ergos). but you can make superb prints as large as you want to go from either of them. that should not be a factor in your decision. 8 is enough, to coin a phrase.
there are real differences in image quality, mainly for low light work. the viewfinder is better on the 5 (but the 30 is good too). IF you can afford it, and IF you don't need 5fps, and IF you don't care about the onboard flash, then get the 5d. but, it sounds like you can't afford it.
the expense isn't just the camera, or even the camera and lenses. the 5d creates huge files, which entails extra costs in cf media, in hard drive storage and backup, and computing power for practical manipulation. you need to factor all of this into your decision. if you decide on the 30d, i'd get the 17-55/2.8 (it is simply the best combination available, and will cover nearly all your needs) and a 50/1.4 for portraits and very low light work. that's it: you could do a whole lifetime of great work with nothing else, and never feel like your glass was holding you back. (most people seem to want long tele lenses for some reason. you can always add that as necessary.)
on the other hand, to get something similar on the 5d, you'd need to get the 24-70/2.8 (larger, heavier, no is) and the 85/1.8 to start (the 24-105 covers an attractive range, but it is a slower lens, limiting your ability both to lock focus in low light and to use the most accurate focussing sensors in the 5d--which you want to use, don't you?), to say nothing of an external flash. your total cost is considerably more, and you really will want to only purchase excellent (ie expensive) lenses to make the most of the 5d sensor.
there is one factor that imo would tip decisively towards the 5d, which is if you want to work with fast wide primes. that was a major reason i went with the 5d. these of course are very expensive lenses (which offer unique capabilities paired to the 5d).
to get the most out of either camera you will want to use manual exposure much of the time, so it's a good thing you are looking to invest a lot of time into this stuff.
so imo it comes to money. if you are willing to spend $5000+ on the camera and have plenty of computing power and storage, then the 5d is a great camera. if you would rather spend around $3000, OR you really like the idea of built in flash, OR you feel the need for 5fps (useful for kids bike and skate tricks, or football, etc), then the 30d is a better choice.
neither one is a compromise, and both are excellent cameras to learn on--they reward advances in your technique and skill (and punish mistakes and deficiencies) without setting artificial limits. you can make beautiful large prints from either one (i routinely go to 13x19, sometimes more); any problems you have in that regard would more likely be attributable to technique or possibly to glass, not to sensor and certainly not megapixels.
enjoy your new camera--the nice thing about this is that either one is a good choice. you can't really go wrong.