Friends are starting up a new business, they want some help. Company is under 20 employees, they all will need Outlook, Excel, also Sharepoint and I will make some PowerApps for them. What MS product should they subscibe to? Cost is important.

Friends are starting up a new business, they want some help. Company is under 20 employees, they all will need Outlook, Excel, also Sharepoint and I will make some PowerApps for them. What MS product should they subscibe to? Cost is important.
For a small business take a look at this comparison page. Compare All Microsoft 365 Plans | Microsoft If they are willing to use the cloud based versions of the office products then Business Basic would be sufficient. But if they want Office on PCs and Laptops then Business Standard is more appropriate.