danryan.us

For the first task, create a 1000 m buffer on the schools point layer. You may want to clip it to the census block group layer (using it as a city boundary layer). It may be graphically more attractive if the buffers are merged into one and made semitransparent.

For task two, a very crude estimate might be arrived at by looking at blockgroups that do not intersect the buffer at all and comparing number of renter units in them to the total in the city. To get a slightly better estimate we might take a union of the buffer and the block groups and then, making the assumption that rentals are uniformly distributed within each block group, use the relative areas of the parts that overlap the buffer and the parts that don't to estimate the number of rentals ruled out by the law.