The answer to this question depends on what you really mean. If you are merely wishing that a way existed to help purchase the home or if you are wishing something you absolutely know is impossible, then you say, “If there were a way, we could help you purchase this home etc.” But, if you believe there might be a way to help and you just haven’t hit on it yet, then you say, “If there was a way, we could help you purchase this home.”