You'll recall the SpaceX honcho basically said he's leaving a light on for any and everyone who wants to move to the Brownsville/South Padre area, work for SpaceX and become a resident of the brand new city he's planning to put on the map.

As it turns out ... people took Elon's tweets as marching orders.

We spoke to agents in the area who say there is a direct correlation between Elon's tweets and an increase in real estate customers. In fact, one agent we spoke to called it "the Elon Musk effect" ... and for good reason.

Shortly after Elon's post, one agent tells us he got a call from a man in Boston inquiring about a rental property in Brownsville. Another agent who's worked in the area for nearly 2 decades said 2 years ago he'd never answer calls from outside of his area code.

Now? Not picking up could be the difference between earning or losing a fat commission. Like on Tuesday, when a man from Oregon called offering to pay $200k in cash for a house in Brownsville. The average median house price in the area is around $167k.

One agent who says he's already sold 7 houses to SpaceX employees says calls keep rolling in from all over the country ... from Illinois and North Dakota to California and Utah. And, if you're curious about Elon's reach? The agent says he got a call from someone in Kenya! It's good to be the richest man in the world.