Is the first negative indication immediately following the Istikharah prayer a result of it, or should the matter be further investigated and inquired into?

The first thing you read after performing Istikhara does not necessarily have to be its result. Rather, entrust the matter to Allah and rely on Him, while seeking counsel from experienced individuals. It is also permissible to repeat Istikhara more than once. If the matter becomes easy, it is a sign of goodness in it; and if it does not become easy, then goodness lies elsewhere. Ibn Taymiyyah said: "So, when one seeks guidance from Allah, whatever Allah expands his chest for and makes easy for him among matters is what Allah has chosen for him."