Field mowing....

5 acres is alot to maintain without the right equipment. Unless you have a lot of time on your hands, it's at best an ongoing project. Is a small estate type tractor with a pto that can run a bush hog in the cards?

I'm split on this this one. As much as I hate weeds, we stay free from what amounts to clear cutting the earth we grow in.

My suggestion of 'Round-up' was just for a temporary kill to rework things to a point of being more managable-not kIll, kill, kill. Permananently clearing could result in other problems. There are of course other brands and diff formulas that kill what you want and for how long you want. Possibly do it in smaller sections, but then you need the 'earth moving equipt' multiple times - which I was guessing you would need to aquire. My understanding was you want to make a large part of it mowable grass and some garden.
As for critters. Snakes will live in just about anything. I just try to keep them away from the house. Had a 5 foot blacksnake trying to visit me in the garage the other day. (3d time this year) I just take them down back and toss em in the woods. Luckily I have never had any poisonouse ones. Rattlers and Copperheads can live in our area but not common. Mostly black, some rat snakes and hognose. My biggest critter issue right now is the rabbits. I've come really close to mowing over a few.