Before I went to bed last night , I started a load of laundry and my dishwasher...got up this morning and my kitchen floor, bathroom floor and laundry area was flooded. No smell so I don't think it's sewage. Any ideas what might be wrong and is it an easy fix or an expensive nightmare...we just bought the house in July 2023. Thanks ahead time for any answers.

put a little food coloring in the washing machine and run a small load just water. be ready to stop the machine if the water shows up.
if the problem is being caused by a blocked drain then its an easy fix.

If the water is coming and coming even after machines stop then it's a supply line leak, turn off all valves in sink cabinet and washing machine valves to examine ruptured hoses or busted connections.

If the flood stops after machines then it's a drain blockage. It may not smell but it's wastewater backing up.

Mop up the flooded area and assess damages. Is the washing machine standpipe wet on the outside? I would first pull out the washing machine drain hose from the stand pipe and pour water down it to see if it backs up. Next check the dishwasher, if you do not have an air gap or the one way valves on the discharge failed you have dirty water in the DW so need to sanitize that. If the DW drain is plugged most likely your kitchen sink is plugged too does your DW drain through a garbage disposer branch? Check all that if that drain is plugged then when you run your disposer that water has nowhere to go when backed up may go back to your DW.

May need professional help to diagnose and remedy.