I have 2 brushed 12v DC motors for my hovercraft and a servo. I need a power source but i also need to keep it lightweight.. which batteries should i go for??? LiPo or LEAD ACID or LiMH??

Lead Acid is out. LiPo or NiMh (not LiMh) depending on your current requirement. Power to weight  ratio is much higher with LiPos.

but will it be able to work for 5 mins..

5 mins., 50 mins. is not the issue per se. You want longer running time you need a larger capacity battery, which translates into more weight and vice versa.

Need more info re: the motor current at maximum load as well as how much weight you can accept for the pack.