the macbook is a good idea. just remember that there aren't as many programs for the mac as there will be for pc.
as far as getting started on a budget, you can use garageband (comes on mac) or download audacity for free. they are both simple and can get you started recording. garageband also has some samples and loops and all of that in there as well for production. i haven't used audacity so i don't know much about it. from there you can purchase a USB mic and start recording.
personally i would look into the Mbox 2 mini interface. it comes with pro tools which is the industry standard recording recording program. it's going to cost you a few hundred, but when it comes to quality, this is one of the best. you get an XLR input for mics, and also two 1/4" inputs which can be for guitars, turntables, beat machines, etc. you may want to use the cheap stuff to get familiar with the whole recording process and everything isntead of investing in something like this for the price.
a mic i really like for hip-hop vocals is the Rode NT1a. i've seen t used on a lot of sessions and it has never let us down. it sells for about $240 or so. i'm pretty sure sweetwater.com has a sale for $225 and you get the shockmount and pop filter with it. again, its a bit expensive, but the quality is top of the line.
sites like sweetwater.com, musiciansfriend.com, and guitarcenter.com often have package deals for recording. you can get a mic, stands, speakers, and any number of things for a package deal. depending on the set-up you want, this can be fairly cheap. all in all you need a mic and probably an interface. you can avoid the interface by using a USB mic. thats really all you need to get started. adding better gear is always a plus. get a better mic, or some more plug-ins to get yourself some more options.
one thing to do is learn how to use everything you buy. a lot of young people will just buy some stuff and just press record but have no idea what else the gear can do, or how to do it. for the best results, do research, learn how signal processing works and take advantage of all of that stuff when you record. Online high school diploma