A friend of ours has just gone through a divorce and is unable to keep her 8 mini horses and has come to us asking if we would like to adopt them.
This is a spectacular disaster in the making, for the reasons others have stated. Number one, your "friend" wants to have it both ways. She is not willing to part with her horses, and wants you to "adopt" them so they can still be her horses. You will do all the work and pay all the money and she will still be able to have her babies and tell you what to do. There is no exit strategy at all. If you decide to sell them, or give them away, or even make a non-approved decision in their care, your friendship will be over. Better it should end before you leap into this folly.
Number two, living on 8 acres has its own unexpected expenses, even without horses. For example, that land, left to itself, will degrade into a patch of noxious weeds that will embarrass you at best, or have the county dunning you for the cost of weed control at worst. Unless you rent it out as farmland you must keep it mowed, at least, which requires some significant machinery. What I'm saying is it would certainly be to your advantage to ease into the responsibilities of maintaining an estate before you take on the additional burden of livestock of any kind, let alone 8 mini horses.
And third, if you have any inclination toward horse ownership, please start with an open mind and a clean slate. The potential satisfaction of owning a pair of well trained 20 year-old quarter horse geldings, for example, might offer a suffering/reward ratio that would be far more faviorable to what 8 minis would provide.