Thanks ezgo & Adam. To clarify this a bit: He3 might be a good solution but I was thinking more like liquid hydrogen, so its nuclear thermal propulsion. It's quite old concept and therefore should be reliable and probably affordable; and also tested by NASA, as far as I know.
If the propellant is not enough (can't calulate it since I'm not a ... ehhhh... well... a rocket scientist) there is possibility to launch some beforehand to Mars orbit (1.stage). Also added some radiators.
Still scifi but as plausible as I can get