Is mass tourism a threat or a blessing for local communities?

I think that mass tourism is a blessing for local communities. Tourist spent in their community a lot of money. People don’t have problems with finding a job. They can work as a guid without any special abilities, because they live there many years so they usually know very much about their city or village. They should only learn sth about history of the city, their monuments and things like that. Even if they don’t want to work as a guide, they can work in a souvenir’s shop. Tourist always want to have some souvenirs. In this community are also many travel agency, in which are working local people. They can also meet some knew interesting people, and learn something about their culture, traditions. Tourists can also encaurage local people to visit their country.
As I said mass tourism is a blessing but it has also some disadvantages. Tourists leave many rubbish. The air is more polluted. Roads are crowded. Local communities have to be kind for touristis even if they don’t deserve it.
Summing up local tourism is a blessing, because it gives work for local communities. Local people can do easy and pleasant work. Although tourists can also have bad influence for local communities and enviroment.