Swarms are temporary clusters of bees handing in a tree etc. These usually happen in spring. It is the natural reproduction of the bees. Half of the colony leaves the hive in the quest of finding a new location. These bees are harmless, and do not seek to sting. They have no brood or food stores to protect. They may hang in a cluster for 30 minutes with up to 4 days (during bad weather). Do not spray these bees with poisons! A beekeeper will usually come and remove them free of charge. Removal time may be as little as 5 minutes or perhaps 30 minutes.
Cutout removals from structures
This is more complicated, because the removal has to do with a full sized colony that can be as big as 200 pounds with bees, brood, and honey stores. Do not use poisons, because the decaying bees and honey will attract other critters. Worse, the decaying material will seep through drywall into your home. Poisons rarely reach the brood chamber and you may only notice temporary relief. Poisons do not resolve the issue and beekeepers will not touch them once poisoned! You will end up paying a pesticide and construction company.
Bees in a structure must be removed correctly. Beekeepers will help you, but the work can take hours and requires equipment. Beekeepers are not construction workers and will not repair any damages like siding or drywall work. Neither the beekeeper or the repair person work for free. Please check with your home owners insurance to see if they cover removal and repairs. Many will cover it.
Expect to pay the beekeepers (usually more then one person will come) 100 dollars per hour for the team. Time cannot be estimated, because the beekeeper does not know how much is involved until they see the actual colony size and location. A vague estimate can be given and many beekeepers will set a cap to the cost.
Beekeepers want to save the bees and are not in it to make money, but you have to understand that they should be compensated for the time, knowledge, and work involved.
Removing bees from structures is not a sure shot for beekeepers. They may have to use a vacuum to remove the bees and the colony is only of value to the beekeeper if they can capture the queen intact. A vacuum can kill her and even without such she can get damaged. That means all the work was for nothing. The success rate is usually less then 50%. Beekeepers will make your sign a removal contract that spells out the work. It protects you and the beekeeper. Please ask question before hiring a beekeeper.
Here is a link to a Generic Bee Removal Contact in Microsoft Word that should be used. Please download and use it.