We use our motor home for a guest house, from time to time, and we "camp out" there, ourselves, when we just need a break.
You can connect an extension cord to your house, if all you need is lights and occasionally the microwave. If you need air conditioning, you will need a heavier duty electrical system. A 30 amp line will probably do it. I have had 50 amp electrical hookups installed here, and at our former stick house. I paid an electrician less than $200 for the job, both times. I suspect that price would vary, depending upon your location.
You can use water from your outside hose bib. You might do better to use the on-board water storage tank. You will want a dedicated white hose, for the potable water.
You can use your sewer cleanout for for waste disposal. There are several ways to do that. You will need to be more specific about your needs, for better advice from our experts.
Don't know what part of the country you live in, but if you have winter, you will have to protect your systems from freezing, and you will need propane for your furnace, for interior heating.
You may have zoning issues. I'm guessing you already checked that out.