In recent years a number of proposals have been made to send astronauts to Mars on a one way ticket. This would reduce the cost and complexity of the trip itself considerably.
Once there, the pioneers would complete the construction of their initial base of operations. Henceforth, they would explore the planet, set up mining and manufacturing facilities, and start to build long term habitation, for themselves and for the settlers that followed on.
And they would never come back.
Now there’s two little problems with this idea.
Firstly, we’re nowhere near to having the technology the experience of living on Mars to set up a permanent settlement. It will take years of return trips, of practice and experimentation on the Martian surface, to develop the capabilities for keeping people alive there for years on end
And secondly, it would be years, probably decades, before the outpost were self-sustaining. Regular supply missions would be needed from Earth. No one, government or private company, would embark on an expedition that would tie them such a huge financial commitment with no definitive cut off point. Governments couldn’t do it, and they probably wouldn’t allow their companies or citizens to do it.
These scenarios, and you can search for them elsewhere on the internet, are at best fanciful and ill thought out, and at worst downright fraudulent.