Always give a actual price estimate even if its a range. If your not sure say I bill out at 30/hr and this might take 10-15 hrs.
I'm a solo also and would never take a 2 day job without giving a number! Probably would say no from start since that's too big of a job for me even with a walker, backpack blower, and tarps.
Maybe before and after pics on jobs like this?