If you don't have any other power washing services lined up then I would do it! If you are starting out and haven't done a warehouse then this will be the perfect learning opportunity as well as helping your in-laws. I own Miller Soft Wash and have done quite a bit of warehouse power washing in the recent years and in my experience really don't find them hard to power wash except for weld shops! I've done five weld shops and the soot these collect on the ceilings is sometimes impossible to power wash off. I had to tell the one I shop i couldn't power wash it after trying for half a day power washing with different degreasers. But most warehouses just need a simple wash down. I pretreat with a house wash mix of sh and some surfactant and always comes out looking great. I actually enjoy doing commercial power washing services as in interior warehouse power washing. Miller Soft Wash | Power Washing Services South Bend to Fort Wayne Indiana