Boiler & AC unit

[Ronald Ty]

Curious, why would there be a boiler unit, in the basement, & an AC unit outside with hvac vents in the main level kitchen? From what I've read, they both have to be independent of each other.

If you were going to flip the house (it would be a high end home), would you switch the boiler for forced air furnace? I would think you'd need to rip out all the boiler pipes throughout the home (it's a tri level). 

Or are there other options?