What happens when two partners who own a business 50% each don't get along and can't agree on anything?

A deadlock -where two equal partners cannot agree on a course of action - is best resolved by the parties. Where it cannot, the partners can voluntarily go to mediation where the partners have the benefit of an experienced third party who helps to determine a partner- driven, mutually agreeable resolution.

If this approach doesn't work, the parties can file an action in state court to extinguish the "deadlock" and the company, where one party or the other asks a judge to appoint a person to manage the venture to keep the assets from eroding, while at the same time trying to figure out how best to resolve the the problem. The company (partners pay for this appointment).

Ultimately based on such an action, a judge can order a company dissolved after an accounting and analysis is completed. If the partners can voluntarily come to some arrangement about who will go and who will stay or if they can find a buyer, its typically a much cheaper and easier solution to this difficult circumstance. The big factor in this process is typically not money, but time. The longer things are in disarray, the harder it is to sell anything.