According to the Bureau of Labor Statistics, 45 percent of all painters are self-employed, though that number may be slightly higher if companies hire freelancers or self-employed painters as part of their team. The price that painters charge for their services is largely dependent on their association and whether the job is completed in the warmer or colder months (painters often charge more in the summer and less in the winter, given demand and other factors). More information regarding painter rates and associated factors is included below.
Back to the article. You can add water to all latex based paints / thinner to oil based paint. The tinting base has absolutely nothing to do with it. Say you are working outside and throughout the day you have to add a little water to keep the same consistency. If somebody really tried to add 20% to 50% water they no longer would be painting they'd be performing a whitewash or pickle finish.