No one compels any one to do anything under the capitalist ruleset, which is simply a ruleset that restricts interactions to those that are mutually voluntary.
And hiring someone and making a profit by employing them to operate your capital (what you Marxists call "means of production) is not "economic rent". The enterprise/capital that enables the labor to produce more value than is expended to hire it is provided by the business owner, and contributes value to the economy.
I strongly recommend you don't base your understanding of Economics on Marxism. Marxism gives no credit to investors for their role in providing capital. Marxism just takes it for granted that capital will emerge, when in reality you need to compensate those who create capital, through the process of saving and investment, in order to incentivize its emergence.
Marxism's non-recognition of this fact is not only a massive oversight that makes the theoretical framework utterly pseudoscientific, it is a consequence of the fact that Marxist theories are totally motivated by an anti-rich ideology, as opposed to the pursuit of scientific truth.
>>If an owner wants to decrease wages of their workers, they may only receive resistance if the workers are unionized
This is totally baseless. Wages for unskilled labor doubled between 1870 and 1900, a period during which unions were extremely weak, and there was a massive influx of poor immigrants to the US pushing up labor supply which would counter-act the economic forces that push up wage rates.
There are other forces that push wages up besides the violations of contract freedom that can locally push up wages for unions. Unlike laws that give unions local monopolies on workforces, economic forces like investment don't depress wages economy-wide. They are positive sum, leading to generalized wage growth.