What should I do with my 401k: keep contributing while my employer will match contributions, or set some money aside to fund my first real estate investment?

Neither option is necessarily a bad choice. It is recommended most often to keep contributing to the 401k, if only to take maximum advantage of those employer matching contributions. You can't roll over those funds while you still work for this company. ​You can, however, roll those funds into a Self-Directed IRA LLC or SoloK when you leave. ​ ​