for my opinion the minimum you can get for professionel use is the canon 20D thats the best for evry type of shoot... if your compare with the invest money.... of course you can get also much better but cost 3 times more ...so thats for the body i thing its enough for starting just to get the feeling if you like it or not after the most important is the lens....
You have to buy a lens who are compatible for full frame 24x36 because canon star already to built full frame capteur and in the case you decide to buy one day this type of full frame body you can still use your lens otherwise its just good for garbadge....
i am not a specialist in canon but for portrait you will need a fix lens like a 50 mm in F1,8 or F1,4::
You don't have to forget with a small capteur like canon 20 D you have to mutiplicate the fokal lens by 1,6 because the format of the capteur.. so with a Canon 20 D a 50 mm is in reality 50x1,6 so 80 mm perfect for portrait...
after depends the money you have but a sigma 70-200 EX DG F2,8 is very good because luminous lens and also very good for portrait.....
after for the small range you can buy a 24-70 sigma ex f 2,8 or tamron 28-75 f 2,8 also very good
all this lens are compatible small and big frame.....
for portrait the 85 mm in 1,8 is also very good...
good luck
i thing because you speack english you can find all your answer in the digital forum
http://www.dpreview.com/