@Wasam Hawari- definitely a tricky balance to maximize the price short of going to market. With that being the case however, you can run a pretty quick and dirty Comparative Market Analysis (CMA) using any of the consumer friendly real estate apps like Zillow/Redfin/etc. Here's a step by step process that will get you a confident range that you guys can base a decision off of that's built on fairly standard appraisal practices.
Step 1) Set the minimum maximum square feet of comps within a 20% up and down range of your home. At 1,300 sq ft, twenty percent equals 260sq ft so set your square foot range to 1,140-1,560.
Step 2) Activate the ability to view closed sales and see if you can limit the closing period to a timeframe of the last 3-6 months.
Step 3) Activate the ability to see Pending listings to give you an idea of what price homes are currently going into contract on. Though you won't know what they will close at (unless you contact the agent and they disclose) it nevertheless provides for one way to try to account for present day market value.
Step 3A) You can further adjust for this by looking at what the list to closing price ratio for the homes that have closed to arrive at a comparable ratio for the Pending listings.
Step 4) Average out the square footage of the Closed and Pending homes and then divide your home's square footage into the average sq ft of the Closed/Pendings. Write this number down.
Step 5) Calculate, if not given, the average per square foot price for both the Closed and Pending properties.
Step 6) Multiply the averaged Closed/Pending square foot price (Step 5) by the square foot ratio that you got in Step 4 to calculate an estimated per square foot price for your home.
Step 7) Multiply the estimated per square foot price for your home by the actual sqft of your home to arrive at a base value. If you completed Step 3A you can apply the ratio to your base value to arrive at a fairly confident (85-95% confident) market price for your home.
Remember however that if the plan is for your partner to either do a cash out refi or a HELOC, they will only have access to a certain amount (75%-85%) of the value of the home depending on the refi/HELOC option. For example, most lenders typically will only provide up to 80% loan to value meaning that for a refi, you can only access up to 80% of the current value of the home minus what you currently owe.
For a home purchased at $500K with a 5% ($25K) conventional loan (loan amount $475K) that is now worth $600K, the numbers would look like this.
-80% of $600K= $480,000
-$480,000-$475,000 (current loan balance)= $5K that you could pull out in equity. I'm sure you're not looking to cash out for $5K.
I say all this as buying you out may require for you and your partner to explore a longer term equity option for you. This could mean you maintaining ownership of a percentage of the rents and equity for a designated period (5-10 years). This option does not provide for you to have access to an immediate return but at least gives you the ability to recoup a more equitable pay out based on the income and equity that is generated by the home if a delayed pay out works for you.
I know that this is a lot of information to digest and so am happy to dive in if you want to send me a direct message. Either way, wish you the best and hope that this info was helpful.