Raise the rent and risk getting bad tenants?

[Jack B.]

Two different houses. One, the guy has rented from me for 7-8 years. I've raised rent once, 3 years ago to bring it closer to market. He has bad credit and can't buy a house, but he can certainly rent a new one albeit with the foreclosure on his record it's harder. I am not big on dealing with hassle this year, but I also have it rented by $500 a month less than market. That's 6K a  year...Raise his rent and risk him moving and dealing with crummy tenants or stay put?

Another rental, 3 software engineers each of which have six figure incomes. I think raising the rent on them by $200 (they've lived there for 2 years) isn't likely to cause them to move, they have chickens and such in the yard, they are comfortable there. 

Raise their rent or not?