Cost to start up a small Barraca

Do you mean a "barraca de praia" ? aka a small restaurant on the beach?  Look at local announce in OLX .com.br.
Be very carreful : not one barraca de praia has legal authorization to exist. So you will buy something that you don't really own. There are also some risk that you buy a barraca which is legal process with owner/past owner. Or a barraca which is already in process to be expriopriated bythe prefeitura. A bit off Fortaleza, they are beaches which are overun by sea; some other where huge sand dunes  make dissapear houses.
Beira Mar barracas are certainly very expensive. Other location in center Fortaleza is Futura Beach. But people go there exclusively the WE (during the day). Dangerous location at night. Dangerous when walking on the beach for away from the biggest barracas (which have got top security). On the side of bairro/favelathe most dangerous in Fortaleza.
There are a lot of pousadas to be sold because it is extremelly difficult to make a leaving of it. A lot of gringoes tried. There are a few big barracas (more like a proper ressort with nice restaurants, swimming pool and mini park aquatic); the other are quite miserable, not sure how they can make money.