Here's some thoughts. Further to what you have decided yourself, go for three pedals and four knee-levers from the start if possible. It'll be easier, and cheaper in the long run, than adding one to a 3+3 setup. The 3+3 will do a lot, but 3+4 setup will do as much as most folks need for E9th work. But if you find an affordable and decent guitar with more - don't be put off, you can "grow into" such machines.
Having said that, the foremost requirement is the sound. Many older guitars are disregarded on account of weight and "old fashioned" mechanics these days, but if you're looking for a reasonable price they can be good value. Emmons have an outstanding reputation but won't come cheap. ShoBuds may be more reasonable but don't forget to check out ZB and even Marlen, they all have devotees; and for good reason. There's mixed reviews on certain vintages of Deckley, MSA and Sierra (soundwise - the mechanics are superb) but they too have their fans - you've just got to use your ears to find the sound you like.
And make sure you are comfortable, can you get your knees underneath, or is it too high for you; can you cope with the string spacing (many older guitars have wider spacing).
Overall - good luck in your search and welcome into the asylum!

PS. on a matter if information, of the guitars mentioned above, I have owned ShoBud, Marlen, ZB and Sierra and found
differences in sound - but have liked them all in their own way.