It is possible to cut down a tree on your property yourself, but it is generally not recommended unless specific conditions are met. You should only consider this project if the tree is small (e.g., under 4-5 inches in diameter and short enough that you don't need a ladder to reach the branches), and you are experienced in handling a chainsaw. The tree must also be located far from any power lines, fences, homes, or other structures. Even for small trees, the work can be dangerous, and it's always advisable to have a spotter to ensure the tree falls correctly and no branches fall on you.

For any tree that is large, requires a ladder to access, or is near electrical lines or structures, you should always hire a professional. Attempting to remove a large tree yourself is extremely dangerous, poses a risk of serious injury, and could result in significant damage to your property.

Before any tree removal, it's also important to check your local and state regulations to ensure the tree is not historic or otherwise protected by your city.

If you’re taking down a tree that you don’t suspect is affected by disease or pests and it’s nowhere near your home or other structures, then calling in a tree company should work fine. However, anything more involved means an arborist is a better option. These pros have years of experience with tree removal and can safely take down trees located next to structures, and they have the tools, sanitization equipment, and experience to remove sick or dying trees without infecting nearby trees. 

Yes, cutting a tree's roots can cause it to fall, particularly if major support roots are severed. In extreme cases, trimming roots can affect the tree's structure and stability. Many crucial roots are located just below the soil's surface. If you make severe cuts to roots more than 2 inches in diameter, you risk impacting the tree's water flow and its ability to withstand severe winds or storms. Even cutting roots less than half an inch in diameter under or outside the tree's canopy can cut off its water supply, causing it to decline, die, and eventually topple.

White vinegar does not kill ivy on trees because its acetic acid concentration is not high enough to overpower it. Vinegar is an effective herbicide for weeds and other plants, but not for the strength of most ivies, including poison ivy and English ivy. You should use an herbicide to kill ivy, such as one with glyphosate, imazapyr, or triclopyr.