i,ll second all the great advice given here.i started with a rebel xt,then a canon 20-d,modified for astrophotography,and my current camera is a 40-d. for glass,of course i started with the kit lenses,that come with the packages,but soon outgrew those,poor,slow lenses.i just traded my canon 100-400 IS L,for a 300 f/4,since a month ago i purchased a used canon 500 mm f/4,a heavy duty tripod,and JOBU gimball head. i traded the 100-400,fot the 300,because the 300 is faster,and will take the 1.4x extender,and still autofocus,and is lighter.
i buy most of my stuff from the U.S.,where excellent deals can be had.so,cody,i,ve often seen canon 350d,or rebel xt,s,for under 400,with low actuations.
i would buy an excellent used body,and buy the best glass you can afford.it,s all about the glass.my 100-400,retails here for about 2200.00,with tax. i bought mine in mint condition,for 1250.00,USD.with duty,exchange,and shipping,the total was 1500.00,CDN,a savings of 700.00!there,s no need to pay exhorbatant prices! just shop around.by the way the 100-400,is a great birding lens,and probably the best zoo lens,out there,with a great range.
my 2 cents
denis