This will avoid the risk of losing a tenant over a rent increase and regardless of how good your tenant is it is poor business practice to supplement a tenants rent.It is not good business to not raise the rent as not only are you supplementing a tenants rent you are also devaluing the resale of your property.Research your local rental market adds and put your rent at market for the size and location of your property.

Adding over a roof with a good dimensional shingle will not devalue the property one bit. it may reduce the life of it from 25 years to 20 but thats it. if its in really bad condition you may have to tear off the old roof but if its not it could save you about $1,000 in tear off costs.

If you are accepting dividends in exchange for asset devaluation, you better have a good healthy bank account. 

Other ways to look at it:  if a duplex has a better cap-rate does it suddenly devalue your SFR?  

Although generating positive cash flow should always be the primary source of profit, you can almost be sure that NJ property will consistently appreciate over time and there is much less chance of devaluation compared to more rural areas.

If you think you have a claim against you title insurance you better hope it is not an issue a survey would have disclosed or they will NOT pay your claim and will be stuck with a devalued and in very extreme cases worthless piece of property.

What are your thoughts on having equity as a safety net for devaluation?

You will make more money listing with a agent even after fees.I suggest you get rid of your tenant before you list as they will devalue the property.

Additionally you want to keep it at market to insure your property is not devalued when you sell if it is anything other than a SFH.

That last sentence is not meant to demean or devalue the advice you'll find here on BP or the myriad books that have been published to give someone like yourself well-honed advice.