A good gauge of performance for a full time rental is roughly 10% of valuation (A $1M home should generate $100K+ in gross revenue.) 

We'd even be happy to move them into one of our (future) properties and just let them keep all/most of their rent income as free cashflow. 

If you ever want to explore other funding options for future flips, let me know! 

Check out this article we wrote, hopefully if can help you in the future.

We don't have kids (might in the future), my husband and I are young and healthy, have stable high-income full-time jobs, and just put in a lot of work to both properties so don't expect huge expenses in the near future.

They just generate chlorine at a constant rate depending on the system setting.  

A project like that will probably take 6 months to 1 year, so what's your expectation for future rents?

When considering 'break-even,' cash flow is included...it's the overall ROI that the property generated for you during your ownership.  

I want to have more rental properties in the future and could definitely use that income to help fund those, but with the interest rates being higher, it makes me nervous.

Your rate will be higher than current, but give you your cash out to use for future opportunities.