Get a tattoo of this restaurant's burger and get free burgers for life

Want free burgers for life? All you have to do is get a tattoo of a burger from Melbourne's Cafe 51.

The Australian burger joint is prepared to shell out free burgers to patrons who get one of Cafe 51's burgers and its logo tattooed somewhere on their body.

"Tattoos are for life, so why shouldn't burgers be free for life too, right?" The restaurant wrote on its website.

Of course, there are some ground rules. Participants must be 18 or older, the free burger can only be redeemed once per day and you'll have to flash the tattoo to Cafe 51 staff if asked. And the burger has to be drawn to scale.

"After launching the promo online on Sunday night, to date we have had over 3,500 entrants," Chris Binos, co-founder of the burger joint, told CNBC "This is way beyond what we expected but testament to our cult following and the bond we have with our customers. We will be selecting the best 10 entrants to get inked."

The competition was inspired by Cafe 51's customers who were tattooing the restaurant's burgers on their body out of "pure passion" for the brand, Binos said.

"This was a fitting tribute to those willing to wear the #burgerlove brand with pride, for life," he said.

The restaurant is limiting the deal to one tattoo per person and it's not clear yet whether you'll have to shell out the money for the tattoo.

"At this stage it is yet to be decided," Binos said. "Originally it was going to be the person getting it done, but after we got one [tattoo] done live on Australian TV on Monday night on a show called 'The Project' it looks like we may get all 10 successful applicants inked live on the show. So, the network may cover the cost. We are discussing this now."

Be careful which burger you choose, however, as Cafe 51 has some monstrous burger concoctions, including the Hulk burger, which contains four beef patties, four pieces of Southern-style crispy chicken, bacon and eight slices of cheddar.

That's a tall order.