Hello friend always,
It is possible to have a healthy relationship if the person is committed to staying in treatment, has fairly evolved coping skills for dealing with stress, and is able to engage in the give-and-take of two-way communication, and does not play games. This is for the person with the schizophrenia as well as the partner.
Your tag is "friend always." Yes, it is possible to be friends with someone who has sz, and it is possible to have a romantic relationship with someone who has the illness. However, I'm not sure that any relationship that starts out as "friends first" for quite a long time will work if the two friends then decide (months or years later) to be lovers, and this goes for people who don't have the schizophrenia as well.
By the way, I second Daughter's response. Though I know people with schizophrenia who have had lovely children (some develop an illness, others do not), I wouldn't get pregnant if I had schizophrenia, nor would I choose to have a family, either naturally or via adoption or stepchildren.
It's a decision I've made, and only I had to be okay with it, nobody else in society has the right to judge me for being childless. I couldn't live with myself if I raised a child and he or she developed the illness.