Snowmobiling is like any other sport the initial start up costs are high, but they are all worth it.
But with sledding you just keep spending, and spending, and spending!
Back on topic..
Another great read, with a little more to it than "Snow Sense", but by the same authors, "Staying Alive in Avalanche Terrain". I reread this book at least once a year, and refer back to it frequently.
And yes, buy a beacon, shovel, and probe. Don't just get the beacon... Then practice. Make it a game or something. Read somewhere that you can use a nerf football, cut it open, stuff a beacon inside (with it on), tape it shut, throw it downhill in the woods, and find it as fast as you can with another beacon. Makes it possible to practice alone, or you can take turns with someone throwing/searching.
I'll ride alone once in a blue moon, for about an hour, on a trail or in a meadow out of reach of avy terrain (need to know the area well to do this, even so, not too wise), to test/tune my sled. And as said in the last post, it isn't very fun, but no one likes to spend an hour at the beginning of a ride so one guy can try to dial in his sled. That was my morning today.
Actually was very frustrated, watched a lone skier skin to the top of a prominent avy mtn, and slowly ski down. I snowboarded there 4 days ago and the snowpack was starting to grow weak (depth hoar at the ground, surface hoar on top, its a N aspect). Now we have a fresh 6", but the whole bowl was cross loaded (very obviously from my distance) so its probably much deeper. I couldn't believe he skied it alone. So I watched in case it did slide (wore my beacon and carried my gear despite having absolutely no intention of sledding on the steep stuff, for this very reason).
Anyway... Start reading, sign up for a class, get to know your sled, figure out which gear you want/need (I recommend Voile T6 Telepro for a shovel, its tough!), and enjoy.