If you received nothing for granting the use of this parking space then it can be revoked at any time but likely the most amicable way to do this is by explaining that your tenants have a need/desire for the parking space and therefore you want to allow your tenants to use the space. 

This town lead right to one of the largest lakes and most desirable houseboating/boating/vacation spots in the country.They have put together a team to help improve their economic improvement plan and are working on incentives to bring business and industry to the area (incentives are necessary in California!)

This growth could likely be attributed to increasing investor desire to gain more diversification within their portfolios.

Multiple perspectives in a room generates more interest and desire- I usually get applications and deposits quicker that way.

It's a nice home in one of the most desirable sections of town, and they don't come that cheap EVER. 

I have a property I'm currently renting to a great tenant for $650/month that's a 2b/1ba and 400sf smaller in a less desirable neighborhood.

This also means understanding thier motivations beyond the days they are looking at properties, thie ability to understand the deal and thier ability as well as desire to follow instructions.

The excel functions VLookup or alike would not work for the desired application.

Of course you can have them qualify lead if that is what you desire. 

Would not concede landscaping forces anything, least of all appreciation.IMO, landscaping enhances curb appeal and thus equates to 'desirability' to the tenants.