He'll have at least $2k per month in positive cash flow and tons of equity when it's time to find the next home in some years.

I noticed on the city website that it can only be done in certain areas, which I'm more than fine with.

It may make sense to save a bit more and invest from a position of power.Keep in mind most helocs are adjustable.

(MLS/Realtor.com is propogated to more than 30 other websites.)David KrulacBigger Pockets Podcast #82  

There are many reasons that adding a single ADU in southern CA is a less than ideal RE investment (i will post a list at the end) but the negative initial equity is a primary reason as the initial negative equity position consumes the initial cash flow and can take many years to recover.As for converting your home to a rental….

But I said at the time that one day I’ll be in a position to take advantage of dropping prices, and I think this is the time.

These platforms can show which amenities are most sought-after in my market, helping me make data-backed decisions.ROI can sometimes be intangible, but even amenities that don't immediately show a monetary return (like higher satisfaction) often lead to long-term benefits, such as more positive reviews and increased visibility on Airbnb’s algorithm 

You state that you have 20% - 25% equity position for safety, but you don't based on the information you gave. 

that we’ve learned in our 24 years, managing almost 700 doors across the Metro Detroit area, including almost 100 S8 leases:Class A Properties:Cashflow vs Appreciation: Typically, 3-5 years for positive cashflow, but you get highest relative rent & value appreciation.Vacancy Est: Historically 10%, 5% the more recent norm.Tenant Pool: Majority will have FICO scores of 680+ (roughly 5% probability of default), zero evictions in last 7 years.Class B Properties:Cashflow vs Appreciation: Typically, decent amount of relative rent & value appreciation.Vacancy Est: Historically 10%, 5% should be applied only if proper research done to support.Tenant Pool: Majority will have FICO scores of 620-680 (around 10% probability of default), some blemishes, but should have no evictions in last 5 yearsClass C Properties:Cashflow vs Appreciation: Typically, high cashflow and at the lower end of relative rent & value appreciation.

that we’ve learned in our 24 years, managing almost 700 doors across the Metro Detroit area, including almost 100 S8 leases:Class A Properties:Cashflow vs Appreciation: Typically, 3-5 years for positive cashflow, but you get highest relative rent & value appreciation.Vacancy Est: Historically 10%, 5% the more recent norm.Tenant Pool: Majority will have FICO scores of 680+ (roughly 5% probability of default), zero evictions in last 7 years.Class B Properties:Cashflow vs Appreciation: Typically, decent amount of relative rent & value appreciation.Vacancy Est: Historically 10%, 5% should be applied only if proper research done to support.Tenant Pool: Majority will have FICO scores of 620-680 (around 10% probability of default), some blemishes, but should have no evictions in last 5 yearsClass C Properties:Cashflow vs Appreciation: Typically, high cashflow and at the lower end of relative rent & value appreciation.