Construction liens are addressed by as statute in Arkansas. If you had a contract and he has followed all of the provisions of the lien statute, he could attach a lien and foreclose to get payment.
Even short of this, he could seek restitution and reimbursement for his work under the theory of unjust enrichment. You would be unjustly enriched by the work he did if you did not pay for it.
Unless there was an explicit understanding that he was doing the work free of charge, if he did not gain anything from the work (some thing in consideration, such as free rent), he would in theory be entitled to some reasonable payment for his services. Under the statute of Frauds the maximum he could be paid is $10,000 if there is no contract that you've signed.
In short, if he did the work, he should be paid unless he said he was doing it for free or for something other than money (something legal, not sex or drugs for example). The amount he is paid should be reasonable for the work he did.
Every legal matter is fact specific, and there are often nuances in every case. This is intended for comment only, and does not create an attorney client relationship.