(1) The primary sources of funding usually suggested for BI are cutting existing means-tested benefit programs and increasing high-end income taxes. (Note that many of these existing programs are currently joint federal/state funded programs, so unless BI was done the same way, this would also involve shifting some spending from the states to the federal government.)
(2) The full single-person household federal poverty line is a very high target to aim for per person for BI in an initial implementation. Half of the two-person household FPL per adult citizen and permanent resident (about $7500/each), and, if BI is going to paid to children (or, rather, guardians on their behalf) the full marginal amount for an additional family member (about $4000/each) per child (again citizens and permanent residents) is probably a more reasonable target to aim for, but I'd expect an initial implementation to start out below that and work up.
(2) The full single-person household federal poverty line is a very high target to aim for per person for BI in an initial implementation. Half of the two-person household FPL per adult citizen and permanent resident (about $7500/each), and, if BI is going to paid to children (or, rather, guardians on their behalf) the full marginal amount for an additional family member (about $4000/each) per child (again citizens and permanent residents) is probably a more reasonable target to aim for, but I'd expect an initial implementation to start out below that and work up.