DFD offer advice

[Nat C.]

Driving for dollars advice sought.

This is a situation I have come across a few times now.

Property owner has a dilapidated multi-family property. They live in the small 'cottage' or 'guest house' whilst the main house is vacant and in poor condition. They've owned it for years and probably inherited the property. 

If I want to try to purchase the property, what is my best approach?

Offer to buy the whole property outright and rent the guest house back to them for cheap rent, which would be not much more than the annual property taxes?

Offer to buy solely the main house which is vacant and sub-divide the land (least desirable option to me)?

Present a low ball cash offer, knowing they are probably going to try to haggle a better price?

Present my MAO (maximum allowable offer)?