Wiring 50 amp RV Outlet to Fuse Box?

No, a properly wired 50 amp is 120/240 four wire.
Problem with two legs of the same 120 leg can overload your neutral.
RV receptacles are tow opposing legs off the electrical service rated at 50 amps each.
They are wired the same as a standard 4 wire range receptacle.
If yours has the old cartridge and Edison style screw in fuses, you should add a separate small breaker box wired off the main lugs.

Hmm...looks like I have some work to do. The house does have a 100 amp breaker subpanel in a different part of the house (newer addition). It does have a physical opening for a double pole breaker, but does that mean that it actually has room for the extra power demand? If not, how do I tell?

Also, it's an additional 50 feet or so away from the location of the RV, would it still be better to add an additional subpanel closer to the original fuse box or just use the one in the back of the house? Thanks, as you can tell, I'm a newb when it comes to wiring.

yes, you can easily make a dual 30 amp outlet that will work just fine. as advised previously 50 amp is really dual 50 amp.
bumpy

No, you cannot use circuits that do not have the legs tripping at the same time. The breakers must be tied together, the fuse must have a single pull for both legs as in OPs cartridge style fuses.
You can add to the existing fuse box with a small breaker panel adjacent to it. It should be connected to the output side of the main fuse assembly.

If you want a 50 A service go to your main panel and find two slots next to each other. Put a double pole 50 A breaker in these slots. Run 3 #6 gauge wires and one #8. 6s are for two hot legs and the neutral and the #8 is for the ground. Install the proper 50A outlet at your trailer. You have full 50A serv. For the trailer. What I did was to put in a 30A plug at our house to keep the trailer plunged into to charge batteries and we would only use 1 Ac IF needed and lights when prepping for a trip. The 30A requires a single pole 30A breaker, # 10 wire, 1 hot, 1 ground , and 1 neutral, and the proper thirty amp outlet. The thirty amp is the way I would go.
PM me if you have any questions

TrekkerB wrote:
To me, 2 50 amp circuits would provide 100 amps to the RV. What am I missing?

Yes that's exactly how it works.
And if you have and older fuse box, you need to run it through one of the "main" cartridge fuse locations. If you only have one of those and it is the input......or your second one feeds something else already.....you are screwed.

Your best bet here is to hire an electrician and PAY HIM for his expertise. SERIOUSLY. You will probably need a branch box installed to put this circuit into.

TrekkerB wrote:
Thanks, as you can tell, I'm a newb when it comes to wiring.

Those who are newb's at electrical wiring should NOT be doing their own work. Dangerous to you and your family.

Time to come out Of the stone age and replace that fuse panel then you won't have wiring issues like subpanels and 50 amp fuses.

a friend wired his own RV outlet box. to His New Georgetown.. took out the refrigerator, 2 flat screen TV's, Stereo Radio... 1 Air conditioner

HE took it as a regular 220 volt system... and fed 220 volts into his RV.

Hire a pro..