has anyone done this before?

im hoping to buy my first house this year and this is what i'd like to do.
buy a house in poor conidition and do it up to how i'd like it. live in it for a while, sell it on and do it again.

but i dont know where to start.
do estate agents get properties like this in?? or is it just auctions.

it dosent have to be a total mess with ceiling falling down and stuff.
just a bit old and in need of most rooms redecorating would be good.