How should I recoup household expenses when Mom lives with me, and she has money?

If she has a Long Term Care policy she should use it. No it won't pay you, but it will open doors to nice facilities. Also be sure to keep her money in an entirely separate account from yours. Spreadsheets are an excellent idea, so add a page for utilities. Enter the total and if it is just the two of you, reimburse by half. I would avoid charging her rent, because then you have to declare that on your tax return as income, unless you are splitting rent on an apartment. Gas, no but use the allowable mileage and keep records of that. The 2014 rate for medical mileage is 23.5 cents per mile. Glad to see you have considered the details.