78' 300d Benz. $500.. oil leak, dead battery Good deal? PLEASE GIVE ME ADVICE

[macias1213]

Hey here,
I just turned 18, and need a car. I have been wanting to get a veggie car since I was 12. Always want to whats best for the world.

I just went and saw a Good Condition '78 300d Mercedes.
It won't start, The battery died on it. The owner said the battery that came with it, when he bought the car died when it got cold, so he bought a new battery 6 months ago, and it died again when it got cold.. What do you think it could be?
The car also leaks oil from somewhere in th middle of the car. Rear seal maybe?
He is trying to sell it for $500, but I think I can talk him down to 3 or 4. The car is Beautiful outside and inn.
I was wanting to convert it to WVO and Bio. Is that a good car to do it on?
Please let me know, you guys are very brilliant!
Best Wishes,
Charan
www.myspace.com/charan1213
charanandreas@hotmail.com