Nobody knows much about the Mexican border wall -- but 300 companies have already said they'd like to help build it.

Businesses will be asked to submit their proposals to design and build prototype wall structures near the United States border with Mexico starting next week, according to the Department of Homeland Security's Customs and Border Protection agency.

Hundreds of companies have already indicated their interest in the project to the agency, which expects to award the initial contracts in April.

Related: Mexican company - We'd provide cement for border wall

They range from large construction firms to small fence companies and security firms. Dozens of the interested companies say in their paperwork that they are owned by Hispanics.

But even these companies know almost nothing about the plans they'll bid on.

"There's really nothing to say at this point. It's all very speculative. Once we get the details, we'll examine whether it's something we'd move on." said Terry Willis of Caddell Construction, which does major government construction projects around the world, including U.S. embassies and prisons.

Related: What history tells us about Trump's wall

Not every company is a serious bidder. One outfit called #ArtThatWall was submitted by a woman named Sarah Zapolsky, who said she just wants to introduce the idea that the wall should not be ugly.

"If America has to have a wall, shouldn't it be beautiful?" she said. "Does it have to be an eyesore, or can it be something marvelous? They're just asking for ideas, so why not just throw out the idea and encourage all my artist friends to do the same."

Trump signed an executive order his first week in office which put plans for the wall in motion, although Congress approval for spending will be needed before actual construction of the wall can begin.

Related: Here's how much Trump's border wall will cost

Trump has said that the entire wall will cost $10 billion, citing an estimate that he received during the campaign from the National Precast Concrete Association. But other estimates have put the cost at as much as $25 billion, according to a report from Bernstein Research, which tracks materials costs.