With the awesome links above, I would love to tackle a bike like this
. Anyways dealing with such bikes in this condition I can offer some tips too if you are going for that "short term" option. Good news is the rust will come off most of the parts and frame. Something that bugs me a little is the rust towards the "weld bead" of the tubes intersecting at the top of the bottom bracket shell. As long as there is no "deep" rust into the frame then it is feasible to fix it up. Just inspect the frame after you clean off the rust.
Way to clean it off fast is get your self a wire wheel bit for a drill if you have access to a drill, spray it down with something like 3-N-1 oil or something like that. Then on low speed hit the spots letting the wire wheel (also known as a brush) do its work.
No drill NO problem. Buy yourself a small wire brush, some packages come with 3 in a pack containing a steel wire brush. brass wire brush, and a regular plastic bristled brush. Put on the oil, rub it into the rust with the brass or steel brush, then work it for a bit, wipe it off, then repeat the process until the all the rust is gone from the frame area. After this process you will immediately be able to tell if there is pitting from the rust. At that point if the frame has been compromised with the rust eating through the frame then I would advise against trying to fix it up. See rust eats the steel (easy way to explain it) and weakens the integrity (strength). That area is vital and critical point of holding a persons weight. It collapses then you collapse with an undesirable and possible fatal end result.
If not then it is pretty easy to do touch-up painting. Now as for the parts I was talking about, is the crank. It looks to be salvageable. The nuts, bearings, bearing cups, and washers I would spend the money on replacing with the link above Nigel I believe posted.
Before taking off the crank make sure the chain is off it. Also spray it with PB blaster or WD-40.
To remove the crank you will need a pedal wrench to remove the pedal by turning it clockwise, the side shown in the picture. The size of the pedal wrench will be either 15mm or 9/16. While you have the pedal wrench in hand go ahead and remove the other pedal by turning it COUNTER CLOCKWISE. Next you will need a crescent wrench (adjustable wrench) to turn the first nut shown on your picture clockwise until it is off. Next is a nut which you probably could get away with using a flat heat (straight blade) screw driver by tapping on one of the notches to make the nut turn clockwise until it is off. As you turn the previous mentioned nut the assembly will loosen up which is normal. Try to wiggle the caged bearing assembly out of the same side. After this you can remove the crank from the other side. Do take notes on the way the assembly was taken off.
Now there is one last nut to be removed. The one that holds the one piece chain ring assembly. This nut has to be turned COUNTER CLOCKWISE to be removed. Using a flat head screw driver is not an option either! You are going to need a bench vise, hook spanner link here...
http://www.amazon.com/Park-Tool-HCW-5-Lock-Spanner/dp/B000C17KRI/ . And alot of strength. After that is off then start the rust removal process as mentioned earlier on the crank, you could probably get away with using the WD-40 or PB blaster, but oil is preferable. How to do the chain ring assembly? This is not easy either, but I bought a baby bottle scrubbing brush that has the small end with the bristles (about $1.00 at a dollar store) and cleaned the crevices with that. The main point is to get all the rust off of the surface.
Now here is some more fun, lol. You have to knock out the bearing races. The two rings left that are pressed into the bottom bracket shell. To do this is pretty simple, just find a hammer and a metal rod. Insert the rod into one side of the shell touching the backside of the other side ring. Press firmly and tap it with the hammer a couple times, move to a different part of the ring tap a couple more times, and keep doing this and it will pop out. Repeat the same to knock out the other ring.
The next step is simple cleaning out the inside of where the parts go by using a couple sprays of that WD-40 or PB Blaster and that baby bottle scrub brush (the big brush) . After you clean that out immediately spray with the WD-40 or PB blaster to get out the gunkies. Have a water spray bottle with dish liquid/water mix (about 2drops dish liquid rest water) handy to spray off crank, chainrings, and the inside of the shell.
Now if you want feel free to spray paint the crank and the chain ring. Let them dry.
To install the new rings you need a tool like this...
http://www.amazon.com/Park-Tool-HHP-3-Mechanic-Bearing/dp/B000VY33TA/ . OR MAKE ONE by reading a couple of this post...
http://forums.bikeride.com/thread-922.html . After pressing them in you will need to put some marine bearing grease or bearing grease on the rings. Put some on the bearings too. Then reinstall your crank assembly in reverse.
Sorry if my directions are confusing but after typing all that I need a cup of coffee lol. Just asked if you are confused.
Bill
Good maintenance to your Bike, can make it like the wheels are, true and smooth!