There are plenty of threads here on the subject and I don't want to veer off of the OP's question, but I think the bottom line is that there isn't a right or wrong answer.

The rest is pretty straightforward so I'll peanut butter over those details since this OP is getting long. 

I'm not OP, but just recently closed on a property with them where the purchase price was $179,900. 

I don't know what people are talking about when they say that rates don't matter right now (unless they are cash buyers, quick flippers, or spam posts - no reference to the OP).

There are those who think the only way to get ahead is to be predatory in every aspect of their dealings. if they can pinch the other guy for a quarter in a handshake they will, pitiful there are such folks, must be in their DNA......not saying the OP is at that extent but there absolutely are people like that in RE.

Would you recommend joining a large co-op like Keller Williams?

The OP is trying to say that the 15M is enough to consider investing in that area, I say there is a more desirable areas if you are only basing on government money spent, I see some 200+M in one building or maybe a parking structure, that is worth buying and holding, perhaps an Airbnb MF or corporate housing, or airline industry clients.

I am in a similar position as David OP.

In any event, I was adding additional perspectives on how the OP could look at the situation.

I am in a similar situation as the OP (Aaron), and am expected to PCS to the area Aug/Sep 2021.