I am having trouble setting a "rent" price for a live in SO in a condo I own.  As taxes and assements have gone up (+special assessments for various improvements...some large), I have gotten a little resentful.  What's a fair and equitable way to set this price?

I will answer this with a little different perspective in mind.  As this rent is coming from a live in SO, are you looking at this relationship as long-term? All "Market Conditions" aside, if the relationship is important to, you need to have a clear and open discussion.  As a Real Estate professional, I could very easily crunch the numbers and give you a "fair number" that would work great for a plutonic roommate, but romantic relationships are different.   If you are building a future you should work out a shared budget and talk about household expenses, so that neither of you resent the other. My wife and I lived together for 5 years before our wedding.  During that time there was a period where I made more than twice what she did, so naturally I paid most of the bills.  Then I went back to school and she paid most of the bills.  There has been a period of unemployment for each of us in the time of our relationship.  Every time we have talked about it, worked out a budget, and we both to this day, feel it was fair. Clearly, it sounds like your SO is okay with the $600, she is currently paying.  If you sit down and explain to her the expenses as you have explained them to us, she  may make it a lot easier by offering a number that she can afford and that you feel is "fair." If you simply throw a number at her, she may either now resent you or move out and then you don't even have the $600 of help you get currently.  Unless you plan on filling her spot with a roommate, I wouldn't calculate the value of your SO living with you like a roommate. From someone who has been there before, approach this by putting your relationship first, if you want a solid relationship in the future.  Clear communication is the key.

If two people are sharing a home, apartment, or any living space, the expenses for that home should be shared equally, or each paying half the monthly costs. So whatever it costs to own and maintain the condo on a monthly basis would be shared equally, which is fair and equitable for both.   Another option is to simply determine the likely market rental value of the condo and simply charge your SO half that amount, as if it were a rental apartment and you were co-tenants on a lease, regardless of any other factors of costs or profit/loss to you.   The last option is more complicated, as you would need to consider the degree of "significance" to you of your "SO" and act accordingly, again regardless of any other factors.

As you're thw owner, all the liabilities associated with it, viz property taxes, insurance, principal+interest should be paid 100% by you. She (live-in SO) should share equitably the cost of using the premises (rental + utilities). You would have to give her some consideration for a fair market value, assuming it's (today's) $2100/month. Longer the lease term, lesser the lease rent, plus calculate the value of the personal considerations. Factor all of these, you should arrive at a figure, discuss the pros and cons, before broaching the subject with her.

I think we need to leave out relationship issues such as how much you make and how much she makes, her potential upside if you sell and buy a nicer place, etc.  The fact is that a comparable unit rents for $2,100/month, so if your goal is "fairness" then she should pay 1/2 of that, and half the utilities.  Your expenses and possible upside as owner should not enter into here. If for some reason you had an extraordinary expense as landlord you would not be able to raise the rent, and if for some reason your insurance or other expenses declined you would not have to lower it, as landlord.  She might not pick such a nice place on her own, but on her own she would be paying the entire rent, so it's OK.  I may be overstepping my bounds and stepping into relationship territory, but it seems to me that someone who does OK should be able to afford $1,050/month rent, and would want to pay their share so as to maintain independence in the relationship. Colorado recognizes common law marriage so make sure she never uses the word "husband/wife or spouse or married" without your correcting her, or you may be totally sharing the upside with her.

I like 's answer better than 's. The issue of comparables is a red herring. In my experience, asking your intimates to pay a figure wholly or partly derived from your personal estimates is asking for trouble. You might as well just avoid all the calculations and say, "Honey, I think you should pay me $1500 instead of $600 in rent, because it would make me feel better."