How did God plan to take care of the Jerusalem believers after they became poor?
God graciously planned to sustain the impoverished Jerusalem believers for the rest of their physical lives through offerings collected from Paul's Gentile converts. Paul consistently took up these collections during his missionary journeys, as Peter, James, and John had asked him not to forget the poor Jews in Jerusalem.
Les explains that the Jerusalem believers had sold their material wealth expecting the Kingdom to come, but Israel did not respond and the Kingdom did not come, so their fund ran dry and they became poor [s359-s368]. Because they had acted under good intentions, God graciously determined to care for them for the rest of their physical lives through the offerings of Paul's converts among the Gentiles [s369-s374]. That is why, during his missionary journeys, Paul continually took up offerings for the poor saints in Jerusalem [s375-s377]. Peter, James, and John, recognizing Paul's coming ministry among the Gentiles, urged him not to forget these poor Jews, and Paul affirmed that they never did [s378-s387].