Can I ask what your budget is? Is this a square acre? A square acre is approx 208'x208'. T-posts are approx. $3.25 (for 5 1/2 ft)for new ones and you will need one every ten feet. So that is approximately $200 - 300 in T-posts. You will need large treated corner posts in every corner and between every straight line if your pasture isn't a perfect square. Your looking at $50 a piece if your doing wood or if you have a welder do them they charge anywhere from $100-300 per corner post! You'll need a bag or 2 of cement for every hole for your corner posts. Here is a website that explains it further.Fence Building - Corner Posts
For the woven or "no-climb" wire its approx. $1.30 or $130 for a 100 ft roll for like 4ft. High. You'll still need to use a stretcher and stretch it. Then you'll need electric wire or tape for the top. All electric fencing is cheaper but your horse will get out alot especially on that small of acreage.
You could do barbless wire its like 1200ft a roll and for 4 strands you would need 3 rolls at $65 a roll or $200 for the majority of your fencing instead of $900. But you will need at least 2 electric wires with it.
Wood corner posts including concrete -$200
No climb wire -$900 (its actually 832 ft but you can only buy it by the roll)
Gate - $100
Other fence materials like electric top wire and insulators - $200
A 10x20 2 sided metal shelter is about $500. You could do wood it will probably cost about the same.
(I know all of this because I just re-fenced 35 acres!)
This is all material only.. it doesn't include labor. This will cost you approx $2000-3000 for a friends property? You would need to lease that land for almost 3 years to be really worth it. I would just pasture board at a place where everything else is taken care of and have the other amenities such as an arena, wash rack, tack room or ect...