It was actually the other way around with me. I got into planes by looking for a place to fly helicopters, as I was already doing tail in hovers on my Blade 400. Helicopters are not hugely supported in my area much beyond the 400 electrics.

You were lucky to get some buddy box time on a trainer nitro heli before you got into it. When I decided to get into helis, I started with the original Blade CX (the yellow bodied FM TX version w/plastic upper head). After little more than a month, I wanted something more challenging and got an AXE CP (BIG mistake, nice for a CP, but a CP in general is not a good choice as a step up from a coaxial). I managed to have it in the air for about 5 seconds before my first rollover crash. That was when the original AXE CP was still a new model (mine was the first one sold at the Hobby Town USA where I was at at the time), and parts support was slim. After spending nearly a year on the sim, and a couple of flights on a Venom Night Ranger II FP, I started to get the AXE back together, but stopped when I got the Blade 400. I spent plenty of time on the 400, as well as a number of crashes. I got comfortable hovering it to the point where, once properly set up and trimmed, I could do small, slow circles with it. I still fly the 400, but I now fly a Hirobo Shuttle ZXX 30 size nitro. That's learning the hard way how to fly a heli. The easy way, get some help (buddy box if possible, but someone to help set up your heli and give you pointers is a huge help as well), start slow, get sim time, and work your way up, as you are doing.

The initial cost doesn't have to be high to start out. The Blade 400 is about the same price as a well equipped RC Nitro (or electric for that matter) monster truck and can be considered a step up from a coaxial or plenty of sim time, and the crashes can cost about the same. The biggest problem is the complexity and difficulty involved in helis. A $500 monster truck, you can just go out and drive. Yeah, you'll crash, but not as soon as with a $500 heli.

As for the 3D heli, if they had someone to guide them, they wouldn't have a purebred 3D helicopter as their first heli to begin with. Going with a nice 3D heli without a buddy box is like going straight to an 89" span Carden Yak 54 instead of a trainer as a first plane (possible, but not recommended and VERY difficult). You can use a 3D heli (such as a Raptor 50 or similar) as a trainer heli with the proper set up on it, LOTS of sim time and a buddy box. However, not many that are new to helis can find a heli instructor to buddy box them.

BTW, as for your sig. I used to race AWD electric TCs. Fun for a while, but once the race organization went downhill with $200-$400 setups being run by noobies racing against $1000+ cars being run by more experienced drivers. I didn't care about winning, but I did want to have at least a chance at it and not be left in the dust about 10+ laps back. That turned me off of cars for a while before I got back into nitro off road again, but just on an occasional bashing basis. If that's your thing, go for it. Just know that there is more expensive specialized tools to setup the suspension on a TC than there are to setup a 3D helis head and blades. If you have a good group to run with, it's great. If the guys you run with are more of the every man for himself type attitude, then it can be a hassle and no fun. Just an FYI.

Happy flying.