Hey, welcome! I always suggest people to start with a low to mid tier instead of going to the flagship cameras, so they don't get frustrated and then a) blame the equipment b) buy more equipment, different brand, and c) give up
So I would suggest you get the K-50 or K-S1. These both seem to have many features. The K-50 is even WR. Why do you want the K-3? I mean, if you cannot name specific features the K-3 has that you need and the lower tier models don't have, then you probably don't need it. Lots of people just assume that if you get a more expensive camera, the photos will look better. That is not true. A camera merely gives you potential to make good photos. Every piece of new equipment has a learning curve, even if you get just a new lens. Getting a whole new system is big, and if you get the most complex things that the system offers, you will feel like you are drowning. You might know about shutter speed and aperture, but you don't know about the machine yet. And a simpler machine is easier to learn. Just like when buying a motorcycle. You start with something not too powerful. Once you get the hang of that, build some experiences and skills, then you can get a real beast and enjoy it.
I would say that unless you have a
need that you can quantify, then don't bother getting a top notch camera. Get a starter camera and invest in good lenses, that is the better way to do it. Lenses are more important, they hold their value, and you can use them on the next camera body anyway. Meanwhile, you get experience and buy the next flagship. There is a new camera coming out every year or two, so you will have plenty of chances to upgrade.
But if you think you want a K-3, go for it. I don't want you to be unhappy with a K-50 and think to yourself some dude on a forum held you back. I don't know you, maybe you would read the manual and patiently perservere and would have no problem starting with the K-3. Either way, welcome aboard and good luck