Hi Justin, To answer this question, it will mostly be based on what your current rate is at, and what your other income is. Your "useable" rental income, according to the bank will be around $825 (see below). So then while you may have some equity, it doesn't mean your debt to income will suffice to pay for another rental property.
I've done 2 different things in this market:
First option is to get a second lienholder on your rental. It sounds like a marketable title, and so that could be a good option. Some caveats here would be that the bank may want you to be incorporated in an LLC, or something like that, if you are specifically investing. You can try Shann Scott at First Interstate for a loan like this, he is easy to work with. This will be an investment or commercial loan. The thing with this option, is that it will create its own separate payment on a new loan, and the lienholder will be in the second position. This is not a place most lenders want to be in, but if the numbers work, then most banks will try to get that loan going for you. These rates will be higher, around 5%, but there is no set in stone rule about these types of rates. But the upside is, you can qualify as an LLC, and sometimes even bad credit doesn't matter that much if the numbers work and the property looks good to the bank.
The second option is to cash out refi. Now you asked about whether your rates will go up... So I had a loan on a property in Bozeman from around 2015, and rates were at 3.8 on a multi-family back then. I just cashed out some equity for another property, dropped my rate to 3.12, and my payments are the same amount, still no PMI, and now I've got more cashflow. It is totally idiosyncratic with each property. If your property is not a multi-family, you may get as low as 2.5 right now, which I would really recommend trying for if you can swing it. Rates will never be this low again in the foreseeable future. Multi's always have a higher rate on them.
So there will be some immediate questions which will pop up at the bank: What is your new debt to income ratio with your new loan that you are wanting to acquire? What is the appraisal going to come in at (you may be seeing comps at $460K, but that doesn't mean the appraiser will agree with you)?
Then the bank will only work with 75% of your rental income towards your new mortgage or loan payments. Also, STR rental income can only be used if you've been incorporated, and paying taxes on that income for a few years in my experience. Any income on your property which is not LTR, will be valued at LTR, which sucks, but that's how it is. So that means you will have about $825 going towards your mortgage, not the $1100.
The bank will sit you down and tell you that you aren't even breaking even, and won't qualify, like this: $185k @ 2.8% (was my guess close for 4 year old rates?) over 30 years, with taxes, insurance = ~$950/mth in liability. So when you want to cash out something, the bank will say, hey, your current property isn't cash-flowing (even if it is). This is mostly because you are only allowed to use the 75% of rental income to qualify on investment property. So you're right at the cusp of paying PMI, at 24.4% equity, and if you take some equity out, you will have to add another $150-$300 of PMI to your debt to income, thereby unqualifying you, unless of course, you have some other source of income.
If you need any help with working with the bank, or finding a multi-family let me know through DM's. No one can answer your question sufficiently enough unless you divulge income and loan rates, which is not something you should be doing with anyone besides your CPA and the bank. But honestly a SFH right now is going to drag you into some big debt in this town!