You can buy US Treasuries right now and some CDs and get 4.5+% return while maintaining the flexibility of keeping low cost debt on the properties. 

I would recommend doing a "reduced" (~60%-70%) leverage refinance which would help drive your rate down as much as possible and hopefully still maintain the cash flow that you would like to have, especially since they are free and clear.If you were to go the portfolio route, I would confirm with the lender you use what their 'occupancy requirement' is.

To thrive in real estate investing, you must maintain a firm grip on your finances.

Financial freedom isn't just about replacing your current income; it's about maintaining your desired lifestyle for the rest of your life.

2) If the lease that the tenant agreed to included them maintaining the front yard/ landscaping - is it reasonable to deduct a 1 time yard clean-up from their security deposit? 

Small, efficient, if properly maintained will last a long time.  

Is it just not my worry what their income is since the voucher covers the rent, or is my concern that if they only have about $950/month then they won’t properly be able to maintain their pets and their standard of living valid?

The only way I would be considered liable would be if I was negligent about maintaining the trees.

If experience is the lone qualification, you can align with a good realtor and contractor and maintain far greater control along with benefiting from all of the upside.

Maintenance Costs are Too HighThe cost of maintaining a rental property—especially an older building—can make selling it a viable option.