There is also statistical and other info...

To start using direct mail with any statistically significant chance of success you'd need to put a few thousand dollars into it. 

Bureau of Labor Statistics.

I would look to your building codes for new units as to the parking requirement, with the ADA, larger complexes will be effected as to the parking count per unit. 1-4 single family may not be covered but that should give you an idea of the statistical requirement based on concentrations.I would want at least 1 1/2 spaces per unit with a 1-4, meaning 6 spaces with a 4plex.If this is "downtown" your market may be different too, many urbanites walk, take public transportation or bike and won't own a vehicle, look to the make-up of the tenant base.Look to comparable units and what parking might be.As to valuation, parking space adjustments will be objective, guess, I would use the cost approach of adding additional parking.

Thank you @Bradley Bogdan it is always good to have statistics to give to my clients.  

These are estimates from the realtor statistics in each given market and the trends and data they provide for realtors comparing July 2020 to July 2021 (August data has not been released yet).

However I think you  may be overthinking this without solid statistics to base this on.

Of course it can be helpful to go to your national statistics agency they often offer interactive maps with demographics as well as income levels and crime statistics. 

I'm naturally biased towards turnkey investing for folks who need to go OOS, but it's definitely not the passive, no-homework investment some people imply.Whether you’re investing out of state or one street over, the number one priority is data - statistical data- on vacancies, maintenance costs, average length of stay, eviction rates and average move out costs, the list goes on. don’t put your money into a new market without getting a firm handle on the data first.

As I always stay, statistics don’t lie.Granted, investing in Mexico comes with its challenges.