It may cross your mind to use a friend of a friend who has fixed a few toilets or painted a house a couple years ago and still has the spray tool. Now, this could save you some money upfront, but it also increases your risk and could even ultimately end up costing you more if you're fixing mistakes or calling in a professional after the fact.
When it comes to making repairs or improvements to your home, there is an inherent upside to using a professionally licensed contractor from the get go. Consider the following:
1. Insurance. This is a big one, as the protection of your home and property should be at the fore front of your mind. Contractors who are licensed are required to hold some sort of liability insurance policy that protects their crew as well as your home from any accidental damages.
2. They have the backing of the State. Almost every state has some sort of dispute resolution program that you can use in the instance that a contractor has wronged you. This could include anything from uncompleted work to damages that weren't fixed. States typically have some sort of regulatory board that manages these cases and compensates home owners for their losses.
3. They can apply for permits. States/counties/cities all require that a contractor provide a valid license in order to receive building permits. These permits also ensure that the work being done is held to a high standard since it must be approved by a governing body.
4. Full Commitment. This one is slightly opinionated, but generally speaking you would expect that someone who takes the time and proper steps to obtain a license in their profession would be fully committed to that profession and providing top level service to their customers. I'm sure your friend's brother is a great guy, but if your repairs are just some side work that isn't important to him because it's not his profession, you may not receive the best results.
If you're contemplating who to use for your upcoming home improvements or necessary repair work, consider ensuring that whoever you select is a licensed contractor in their profession. It may seem a bit more costly upfront, but it will minimize your risk and save you from potentially spending hundreds of dollars fixing an inexperienced person's mistakes.