If you intend on coming to Peru for a business trip, or temporarily moving to Peru for business purposes, then you will need to obtain either a business visa or a temporal work visa. The maximum number of days for a business visa is 90 days, it cannot be extended. A temporary work visa will be issued for 90 days and can then be extended up to a year. Obtaining a business visa is especially important if you intend on signing contracts or other official documents while in Peru.
If you intend on moving to Peru to work and do have a work contract for one year at least with your employer in Peru, then you might consider applying for a Carnet de Extranjería. Most of the time, people enter on a tourist visa and then process their residence card once they are in Peru.
You won´t have to apply for the tourist visa - it is a stamp they put into your passport when you go through customs in Lima or at the border if you enter by car or bus from a neighbouring country. The maximum length of a tourist visa is 183 days per year.
Once you are in Peru, you will need to make many trips to Migraciones to apply for a work visa which is valid for one year. Your work visa is called a Carnet Extranjería and can be renewed each year for a fee, given the fact that you are employed in Peru.
Having a Carnet has fun perks, like free entrance into some Inca ruins and other tourist sites in Cusco, as you are considered a legal resident of Peru and not a tourist.
Click here for more information about how to obtain a business or work visa.
The short answer is yes. Many foreigners enter the country on a tourist visa and find a job in a restaurant, bar, hostel, or as a private English tutor. They get paid under-the-table by their employer in cash, or receive direct payment from their students in cash. Unless your employer is being checked by the police, there is a great chance, that you will never be discovered.
In the past, many foreigners have stayed in Peru, sometimes for years, leaving and entering the country (e.g. to Bolivia) and renewing their tourist visa over and over again.
Recently however, Peru is making efforts to avoid illegal workers in their country. It is no longer possible to stay longer than 183 days as a tourist in the country per year and the fee for overstaying your tourist visa has been lifted.
If you are planning to stay longer than half a year in Peru working or engaging in some other project, it is advisable to apply for a Carnet de Extranjería or temporary work visa.