The honest answer depends almost entirely on the size of the tree and what surrounds it. A small, isolated tree is a reasonable do-it-yourself project for a careful homeowner with the right tools. A large tree, or any tree near a structure or power line, is genuinely dangerous work that belongs to a trained, insured crew, and the line between the two is worth respecting.
For the small end, think of a young ornamental or a slender tree under roughly fifteen to twenty feet, standing in the open with plenty of clear space to fall and nothing valuable beneath it. With a chainsaw you know how to operate, proper protective gear, and a sound understanding of how to make felling cuts so the tree drops where you intend, a homeowner can take down a small tree safely. Even then, a clear escape path and a second person watching are basic precautions worth taking.
The risks escalate fast as the tree grows. Large trees are heavy and unpredictable, and the most common ways amateurs get seriously hurt or killed involve exactly this work: a tree falling the wrong direction, a limb dropping unexpectedly, a chainsaw kicking back, or a fall from height while trying to reach the canopy. A tree near your house, your neighbor’s house, a fence, or a power line raises the stakes even further, because a mistake damages property or, with power lines, can be fatal. Power lines in particular are a hard stop. Never attempt to remove a tree touching or near electrical lines yourself, and call the utility.
Money factors in too. A professional crew carries general liability and workers’ compensation insurance, which means that if something goes wrong, you are not personally on the hook for an injured worker or a crushed roof. Doing the work yourself puts all of that risk on you.
When in doubt, the safe default is to hire a professional and get a few estimates. The cost of a removal is almost always less than the cost of a serious injury or a tree through your roof.