Where did the poor saints in Jerusalem come from?
They were Jewish believers who had likely come to Jerusalem for Passover or Pentecost from places such as Babylon and Rome. After giving all they had to the common fund, they stayed and lived off the kitty, unable to afford return travel.
Les teaches that these poor saints were in Jerusalem because they had given everything they had—cashed in their CDs, sold their land and houses—and put it all into a common kitty in Acts chapter 2 and 3 in light of the Kingdom. But the Kingdom did not come, because Israel rejected it. Les imagines a lot of them had come for Passover or Pentecost from maybe Babylon and Rome, got involved, gave what they had, and did not even have ship fare home. So they lived off the common fund, and God in His providence cared for them through the offerings of Paul's converts from Gentiledom brought back to Jerusalem.