That's not going to work too well if you have extremely limited resources, mate. Your safest bet is to go with a major brand like Dell or Gateway, just to give two arbitrary examples and pay for an OEM version of what you are looking for that will work well from the outset or the Service Plan will cost them, which is not compatible with the bottom line if they sell you something that does not work acceptably.
A refurb with known stability and limited upgrade possibilities, a barebones with minimal (component-only) guarantees but many later expansion options, or factory-built with known compatibilities that absolutely will work -but is not the cheapest way to go.
Got to decide on only one path, mate.