In this specific case I think it means "to pursue career in real state"
"Sign up" could be both, meaning "taking into an organization" or "joining (affiliate) with an organization."http://www.thesaurus.com/browse/sign%20up/2
See a similar approach, from the headlines "Military spouses, Retirees Sign Up For Real State Careers.
Source: Rome News Tribune -on June 8, 2007.)https://news.google.com/newspapers?nid= ... 2&hl=pt-BR
like we signed up for a lifetime in real estate?
In Portuguese, by my loose translation could be, "é como se entrássemos na carreira imobiliária para sempre/pelo resto da vida/por toda uma vida." (carreira de negócios imobiliários - ou coisa assim.)
After you have read this post, you can give the site Linguee a stab with the keywords "real state".