Silver soldering (high temp type) can produce very strong joints suitable to almost any application. There is a caveat, tho, that the joints must be properly designed. Many racing bicycle frames have been silver soldered or brased, that is a testiment to the strenght available in the processes.

You've not given us a very good idea of the sorts of joints you will be making, so it's hard to answer your question in that regard. You say landing gear for large planes, I assume you mean 20 poundish giant scale aircraft. With properly designed joints, silver solder could be adequate.

That said, brazing and silver soldering are techniques that require some finesse and experience. You would need to make an investment in time and materials to practice with, and in fact, an experienced instructor would help. At a minimum, you'd need:

Various grades of silver solder (it comes in different melting temperatures. You use the highest temp stuff first, then go to the lower and lower temps as your assembly progresses, thereby not melting the previous joints).
appropriate fluxes
An oxy/acetylene torch, or at least an acetylene/air torch with appropriate nozzles and tank (s), hoses and regulators.
some things to solder together
lots of time to practice.
A suitably ventilated area to work in
fire extinguisher!

Silver Soldering and Brazing require pretty much the same skill level as welding, this isn't lead/tin soldering. You'll need to invest a couple hundred dollars to get going.

A simple tig setup would run you a little shy of $1000, and then you'd need much practice. If all your work is aluminum or steel, a small mig setup (about 5-600 with gas) might be adequate, but tig does finer work.

Have you considered the machine tools you'll likely need to make gear struts and such? Their costs will likely outstrip your welding equipment costs by a large margin, unless you're building very simple tube-to-tube-to-bar assemblies.

Might be cheaper to just buy Robarts or something. There's a good reason why they cost what they do!

Good luck!

J