The rule of thumb for a properly designed and constructed 532nm DPSS is to expect about 20% green output for 808nm output of the pump diode (i.e. 1W @ 532nm requires a pump diode on the order of 5W @ 808nm.) Keep in mind this is the general efficiency of a properly manufactured laser system and is only an average. Higher efficiencies are common but so are lower efficiencies. If you plan to build your own expect a low order of efficiency unless you fully understand the mathematics of the optics required, including cavity design. You can then make a reasonable prediction regarding the expected output. Even then, you could be surprised.
I don't recommend end pumping unless you just want to see if you can do it. Side pumping, as an enthusiast, is a better and easier solution because of the availability of diode bars at reasonable prices and the physical configuration of the resonator is easier to fabricate. Once you have a diode pumped YAG or YVO4 laser working then you can introduce the KTP for frequency doubling. This requires some mathematics as well as test data to determine the best size of KTP as well as proper orientation.
If you have the time and the money it might be quite satisfying to build your own greenie.
