My husband and I are looking to buy an old home- but we have some concerns abut the main electric panel (with the breakers) being located on the outside of the house? Will this pass inspection and if not- how expensive would this be to repair? Is this a deal-breaker in a professional's eyes?

The NEC (National Electric Code) allows for the placement of the Main Service Panel outside as long as the Panel Board is inside "Weatherproof" cabinet.

You should be fine. In case you are really worried, you can contact the AHJ (Authority Having Jurisdiction) electrical inspectors to make sure that there are no local code prohibiting an outside Main Service Panel.

In some places, like the southwest and California, this is SOP.