The best way to find those values is either to ask a local knowledgable realtor, or to extract them by doing a comparative analysis on like properties with one that doesn't have that particular feature, and the same way that you wold do a CMA.  

OK, I'll play devil's advocate to Jon's advice on extracting equity from your personal residence.

When you transfer title to a partnership (LLC), you might be adding additional risk if your partner has creditor's trying to extract payments on bad debts or even a judgment.Another way for you to do this is a joint venture agreement.

If you apply the usual goal of extracting $100/month/unit from $300 in rent, what's left for expenses and debt service is only $200. $150 of that is expense (50% rule, which I assure you applies to these properties), leaving only $50 for debt service.

If you want to extract $100 cash flow, that leaves only $50 for a P&I payment.

I had a tooth extracted this am, under the ibfluence of some good meds (LOL) so that's my short version, bottom line, I suggest your time will be well spent looking at your own long term properties.

This is why subscription agreements have an attached investor suitability questionnaire that dives into the investor's background to extract whether the investment is appropriate. 

@Jim Zatko Congrats on taking the leap and your ability to be honest with yourself in order to  extract the lesson from your first experience.

I think J Scott did a great job in defining how we as investors extract value and why we seek out real estate as an investment vehicle.

Yes, you can extract money from it to invest elsewhere.