SAO PAULO, July 29 (Reuters) - Banco Santander Brasil SA , the nation's largest foreign lender, is in the final stages of negotiations to create a joint venture with consumer lender Banco Bonsucesso SA, a source with knowledge of the situation said on Tuesday.

A joint venture should help Santander Brasil, the local unit of Spain's Banco Santander SA, to expand in payroll-deductible lending, said the source, who requested anonymity because the matter is private. Santander and Bonsucesso did not immediately comment.

The Pentagna Guimarães family, which founded Bonsucesso in 1992, has also helped the lender expand in lending for small- and mid-sized companies.

Veja magazine's Radar column reported the deal early on Tuesday.

The structure of the Santander Brasil-Bonsucesso venture is similar to one signed in 2012 between Itaú Unibanco Holding SA and payroll lender Banco BMG SA, according to the source. BMG was founded three decades ago by relatives of the Pentagna Guimarães family.

The Itaú-BMG deal called for a new company to get 1 billion reais in capital, with Itau contributing 70 percent and BMG supplying the rest. Itaú also agreed to provide unlimited funding to the joint venture and 300 million reais a month directly to BMG over five years to fund origination.

Shares of Santander Brasil rose 0.9 percent in midmorning trading in São Paulo.

(Reporting by Aluísio Alves and Guillermo Parra-Bernal; Editing by Lisa Von Ahn)