In reply to joshtee25:
Yes, I would say renting a car is the best way if you want to get out in the wilds. I guess you'll want 4WD. However, it is surprisingly expensive, both for vehicle hire and fuel (I think petrol is now more expensive in Malawi than in the UK). Be prepared for plenty of road blocks at which you need to show your licence, and also for many, many speed traps. Also watch out for car hire places which only offer 3rd party insurance.
Not sure how well sleeping in the car will work. Malawi is densely populated so you can be pretty sure there will be people living all along most roads, and you will be an object of some interest. I imagine people will find it very odd that someone of your (comparatively) great wealth would sleep in his car, and although Malawi is generally quite safe it's possible you might have some security concerns. Haven't tried it though, so you might be fine.
Sounds like a great trip! Enjoy.