If your question refers to it: Marxism is an analysis of the social structure of market economy. It doesn't work as a guidebook for individual behaviour inside of market economy, but for collective emancipation from a social order that results in exploitation.
Doing so would mean decide collectively/democratically over the collaborative use of the means of production.
"I'm buying some means of production with my money" and "their fields" is a market economy situation.
You don't go from caputalism to socialism by individually changing your personal economic behaviour, but by changing social order.