While it may be expensive and time consuming to find the right horse. When you factor in breeding soundness exam, stud fee, shipping/marecare or AI, ultrasounds, vaccines, foal watch, feed, training, hoofcare its actually cheaper to buy a horse then breed one.
Problems with mares may be rare for some, which might be good luck or good planning. Its probably both. Horse delivery drama tends to make up for it in the short life for emergency response. The time between the start of birth and death is about 40 minutes for a foal. So, by the time you realize you are having a problem its not a matter of saving a foal but of delivering a dead one. Then you hope really hard that the mare lives.
There are good chances that your mare would deliver without a problem; however, there is risk in everything. I would not want to breed a 17 year old maiden mare. The toll it takes on a horses body is significant and maiden mares can have difficulty with conception plus age. I guess the question is what does your mare bring to the table? Great genes? Great conformation? Great show record on a national stage? I would make a list. Your own personal list. Reasons to breed on one side and reasons not to breed on the other.