Basil starts well just with regular house temps, I have found (60's night, 70's day) My thermostat is below 70, but one area for seeds is warmer with lights and near heat register They take up to 5 days, with heat mat 3,
As for setting out, basil doesn't like below 40, and just never seems to recover if out too early in spring. I would plan for 6 wks to planting for small plants, 8 wks for bigger. Of course you can put the plantlets out to harden especially during the day in sheltered spot before planting.
I like some fresh ones coming along also. Hopefully you will not get the dreaded downy mildew.