If you were going to come to my house, there are 2 ways i can ask you to come.
1) I can ask you to take a public bus which drops you near my house.
2) I can send a car.
.com domains or even your own branded subdomains are cars. They are polished and elegant and in your control. Free domains are public buses. The policies of those domains are not in your control. I am saying this because i see that you are in the business domain and write about businesses. So i would recommend using paid domain only.
Please do a search for any competitive keyword and let me know how many .tk domains do u see in the top 10 or on first page of google Just a suggestion