You'll have the promotion fan bonus which means that for next season only you'll be able to support a higher salary than the rest of your league, especially with that sweet arena of yours. I'd aim for a PF something like 10/7/4/4/7/7 15/14/13/8 probably around 60k salary. Towards the end you'll wanna boost up with an even better center. This is what I did and even though it took me two seasons due to injury's it got me to D2. Just my two cents, if you have the money and the arena riding the promotion wave is the new easiest way to shoot to the top.
Being able to support a higher salary is nice, but even better is being able to support a higher salary, not needing it, and making tons of cash every week. I just don't see what the hurry is. If he waits to add salary, that is guaranteed money in the bank for each week he waits, and worse case he might lose an early game or two which really won't matter in the grand scheme of things (very minimal fan impact coming off a d4 ship). Besides the money benefit of waiting, it will also allow him to customize his upgrades to the strengths and weakness of the best teams in his division instead of doing it blindly, which can be a huge advantage.