Forward them the letters so they know you aren't making it up and then have them sign an addendum to your lease that states if you get another letter from the HOA that you the landlord will hire a professional landscaper to come and mow the lawn at the tenants expense. 

I easily spent a few thousand just on landscaping. 

My concern with interlocking vinyl would be joint expansion consistent with Hot water hitting it but not equally.

I know that in some areas there are landscape designers that will do this.

New Law Allows Three Housing Units on Every Parcel in CaliforniaStatement from California YIMBY President & CEO Brian HanlonSacramento, CA – Today California YIMBY released the following statement celebrating the historic passage of a package of bills that could triple housing supply in the state:“The passage of AB 68, along with SB 13 and AB 881, fundamentally shifts the landscape for building new homes in our state,” said Brian Hanlon, co-founder and President of California YIMBY.

Without seeing it, it is difficult to tell you but I think you could offset the cost with landscaping and curb appeal. 

You can always call individual sub-contractors (Roofers, electricians, tile workers, cabinet guys, countertop guys, painters, landscapers, HVAC techs, etc) and just ask over the phone for at least a ball park estimate of what the costs are.

Deal Numbers:3 Bed, 2 Bath -  Approx 1,450 sqftPurchase Price: $45,000Expected ARV: $115,000Rehab Costs: $45,000 - $50,000 (2 holes in roof - somewhat sizeable but covered; moderate gutting of inside will need to be done; plus some landscaping)Expected Rent: $1,100/monthTaxes+Insurance: $1,900/year

Here in MA, I've seen then as low as $75 for bare minimums - exterior maintenance, landscaping, snow and trash.On the high end, I showed a former sea captain's mansion in Dartmouth MA. 

Redo landscaping Front / Back.