Haha Mistawasis - calm down a little~ it's not as bad as you soon, sorry if I made it sound scary! (have you ever heard of new fish owners adding like, 10 fish at a time and they all died? Guess why! Hint: Ammonia. Lol)
A betta's amount of space will ALWAYS end up with different opinions. I divided mine (5 gal) and it's okay if you do too, and welll, you have to know anyway. Is it a hex though?? Don't divided a hex
Heating is great. Getting a filter is not necessary, but if you want to cycle it's much better. Beneficial bacteria (which keeps ammonia and nitrates down to 0) grow absolutely WONDERFUL in a filter cartridge that's big enough. If you do end up buying a filter, not saying you have to, get a filter cartridge with no carbon. I'll explain why later to make the post shorter.
I understand the fish in- it's simpler, you might get yelled at, but I doubt it, unless a mr. grumpy walks in, hehe. Just as long as you do enough water changes, you'll be fine. Now, since you're adding two in, here the deal: You really should do 50% water changes daily, or every other day. You have a siphon, right? So much easier to do that.
Speeding up cycling! Heres a couple ways.
1) Other people's tanks. BTW, getting cycled water is hardly anything. The benificial bacteria lives on surfaces. Ask for one or two ornaments. If you take too much, or you take their filter cartridge, THEIR cycle might die, or go into a mini cycle.
Also, gravel. Get a pantyhose that's never seen soap before and get a nice handful of gravel (don't disturb their gravel too much, it might land a mini cycle as well) and put it in the pantyhose and put it in the tank. This helps a lot too.
I think thats it?
And for a ready tank, in your case, that just means: Have the tank running. Put in treated water, turn heater on, and that's about it really. Oh, but obviously add all your decorations too. IT's just to check for any malfunctions. (and I recommend getting lots of plants as well. My bettas showed improvement when I added a bajillion plants in). What I consider a "must have" with a betta is at LEAST 1 large plant/cave for the betta to hide in, and 1 other plant as well.
And heads up!! If you go to an LFS and they tell you one thing or another, check with this forum! LFS are 90% of the time plain wrong. Especially in my own experience.
EDIT: 1fish2fish beat me. Lol