The first thing I would advise is to make sure you can stand to lose the money you give your brothers. Most owners succeed because they wonít eat if they fail. When something breaks, the owner still has to figure out how to get the job done. This business is tough and it will be hard for your brothers to make it if they are expecting you to bail them out of trouble. I would be much more concerned with their commitment level than their ability to fix equipment.
Sorry to get into your personal business....now to answer your questions.
1. If they have the desire and commitment to be successful, then they will figure out how to get equipment fixed. I doubt many new owners start out knowing how to repair all of their equipment in the field, but they quickly learn to repair what they can.
2. Find a good shop that can make repairs and return their equipment in a timely manner.
3. Don't worry about doubling up on equipment. Most new businesses do not have enough work to worry about a little down time from a broken piece of equipment, plus you can always rent in a pinch.