Hey Ruthie, (sorry, how can anyone resist saying that? :B )
What can be done would depend on how long you plan to do this and how much money you want to spend to make it more livable and bearable in the temp. extremes you'll have where your are. $$ can start to add up if you want to do all the right stuff.
This made me think of the article in the latest Trailer Life magazine where a guy lived in a smaller TT by himself through one winter up in the Yukon. Pretty extreme and a fun read on how he handled it.
You don't need an actual "power pedestal" like in a campground. You can get a 30 amp RV receptacle installed in a 4x4 PVC outlet box and mount it on wood post. If you end up using an extension cord of some type, don't have the plug & connector exposed to the elements. Same if you mount a 30 amp recept. on a post.
Heated underbellies are very inefficient because a duct(s) goes directly from the furnace into the underbelly and then goes into the outdoors. You will find yourself going through a lot of propane and the furnace running a lot in the winter (noisy too). There are electric heating blankets that can be attached to the bottom of a tank, but you'd have to remove the underbelly material to do that. Then you'd also have to install heat tape and maybe insulation. The best thing to do would be to start with a true 4-seasons (aka polar) model and I believe some have an option of ordering the tank heaters. A proper 4-seasons TT has thicker walls and substantially upgraded insulation throughout like the
Outdoors RV Windriver for example.
If you're buying a used TT and it's not a 4-seasons unit, I'd install plywood skirting around the perimeter down to the ground. Rigid foam on the inside of that will greatly reduce heat loss. Would be a good thing on any TT too. This way you could run a water line right underneath so it won't freeze up.
I would plan on using an oil-filled electric heater or a cube heater to supplement the furnace. Oil-filled is noise-less and would allow you to hear the TV. You will want "solid" voltage too. If it tends to drop often and gets too low (which is more likely in a rural area), you can have problems. I'd get as a min. a simple plug-in voltage monitor. Best is an EMS unit (Progressive Industries or TRC) that automatically monitors the power and will shut down if needed. You need to consider the overall length of run between the TT and the panel in the house and maybe out to the street. What is the wire size to the garage? You'll be adding another 30 amps on top of what's there now. You CANNOT connect to 220 volts - MUST be 120 volts only if you have a 30 amp service in the TT. If it is a 50 amp, 220 volts is okay but you MUST have a 3rd wire for a neutral present. Make sure all grounding and bonding is up to snuff for safety reasons (ask your electrician). Might even make sense to run wire/cable directly from the house to the TT (ask electrician).
You should look into how to reduce moisture buildup inside in cold weather and along with that, ventilation. Good thread going in this forum at the moment.
You could get a 500 gallon or so holding tank buried in the ground next to the TT to dump the black tank into. This would greatly cut down the number of visits and costs of a guy going out to pump your TT out. It's okay to leave grey tank valves open but only if you have a sewer or holding tank in the ground. The only way to avoid not having to deal with a black tank valve all the time would be to install a residential flush toilet in place of the RV type, which can be done but a lot of work. And if flushing into a holding tank in the ground, you're flushing more water into it than an RV toilet. If you installed an in-ground holding tank, you'd just get an ordinary septic tank pump truck in. Call one and find out how much they charge per visit.
Does the old house have a septic system? Is it up to adding your RV to it? You can always add a cleanout fitting if you can find out where the piping is buried. Code has required an outside cleanout in recent years but probably not 60 years ago. If there is a septic system, you may want to get the tank(s) pumped out. They normally should be every couple of years and you don't want problems in the dead of the winter.
Have fun.