Part 3:
I have 4 wheelchairs. One was bought by private insurance (C500s VS). I have purchased 3 of them privately from craigslist. I have paid between $500 and $4,000 each for the used wheelchairs, typically spending another $1,000 each to get them sized properly for me.
Permobil makes snowtires for the drive wheels. They are great in snow, but also provide added traction on grass, dirt, and mud.
And, if you to take the next step, you could consider a four wheel drive wheelchair. Mine is the Magic Mobility X4 (about 15 years old). The current model is the X8 Extreme, which is better in every way. These come with 14 inch ATV pneumatic ATV tires, which are wonderful outdoors. While the wheelchair can be used indoors, it is not really all that practical to do so. It would be great for getting around the work site and storing in the toy hauler's garage. Be aware that they are a bear to back up in a straight line.
We met us on an other forum a few months ago. You'll recognize my profil photo and my X8.
Today my X8 is a very very well 4x4 wheelchair. Since last September I installed 10 (yes ten) 3.2v/240Ah LiFePo4 cells. Charging them with the very good iCharger 4010, or the small but strong X12 from iCharger too.