To lease the first house,I would want a much longer lease than 6 months. My FDC lady said it cost her anout $3 -$3500 to set her place up. There had to be shatter proof film put on all the windows in the kids areas (bottom 1/2) pool fencing around the play area, and kid proof locks everywhere. she also put in a sandpit. She got a grant of something like $1800 but I think that is just a one off thing.
It would be such a shame to go to all of that effort and have it sold form under you.
Also, I dont know if you would tell the parents, but, I would have to seriously consider weather I would put my DS in daycare that may only last for 6 months and then have to be relocated to either an inconvenient area or shut down for a month while moving.
GL though, have you considered maybe paying a bit more by moving to an area that has high wait lists for FDC and that way you would be able to fill up on your quota of after school care too?