You need to research your fencing (and how to do it) very thoroughly before making any purchase decision. A fence should last 40 years, and it's lifetime dictated by how long the posts last, not by how long the wire does. Wire should last a lot longer than the posts.
Class1 galv often begins rusting within 5 years. Class 3 galv will be rust free up to 15 years..maybe longer unless it is exposed to a salt air environment.
I do understand, that initial costs and outlay can be intimidating, but buy the best wire you can find and the best posts you can find. Not all woven wire is created equally. Some, will not follow uneven terrain very well, others will without any strand being loose.
You should be able to get woven wire to stand on it's own when you tension it.
You can by the way, buy woven wire in 600' + rolls.
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If I were going to install goat/sheep fencing, it would be Tornado 1348-12 12.5g fixed knot HT with 1 or 2 hot wires above the net fence. HT stretches tighter, lasts longer, and requires fewer posts.
No, it isn't inexpensive wire, but as with anything permanent, you want to divide the cost into the years of use you will get before need to replace it.
I suggest you look at some Youtube videos posted by someone named Farm Fence Solutions out of Indiana. He knows his stuff.