Should you invest in some kit so you can train indoors? Well, you could save your pennies and spend the entire off-season running or riding outside, especially if you mix up road cycling with mountain biking and trail running. But even then, there'll be times when you'll be beaten by the weather. Without indoor kit there's every chance you might miss a session. With it, you can tick off every session.
So the key item you'll need is a turbo trainer. These are perfect for those of you with children where you can babysit atop your saddle! Just note that if this is you, spend enough to bag yourself a quiet trainer. We've tested ones in the past that are off the decibel scale.
Also, remember that as much as us triathletes cherish a pain cave, many of us simply won't have the garage or room space to create this training