That's a big decision for you to buy a house and by taking a loan adds extra pressure on you. As you mentioned you have less trust in the longevity of your relationship so I think you are afraid to buy a permanent house by taking a loan and you are afraid to have to cover all these loans by yourself. If that's the case then you should eliminate this uncertainty about the longevity of the relationship. As all, I can say talk with your partner and ask her/his opinions and share your idea of buying a house together.

Further, the amount you told of rent is high as compared to our country like here the rent for a whole house having two to four rooms with Washroom could range from $50 to $100. which is not that much. Before making a permanent house you should clear your to mind about what use it will be after you, like if you are planning a family having kids then go on and make that house because in future that will be an asset for your upcoming generation for which they will praise you because future has its own problems that could make economic conditions more bad but now as you said, you are getting some interest covering schemes than you should buy it.

If you are not planning for a family then it's ok to live a loan-free life because taking a loan and giving huge interest on it becomes a neck noose for you. This was my thinking but the decision is your own plus I am not in favor of taking interest base loans, like when we made a house we ask for loans from relatives and friends (interest-free). You may get fewer loans by this but it's tension free.