@Zachary A. Hey, my husband is active duty Navy and he does alot of TDY's. So I definitely understand this world and what you are trying to do. I have heard of a few places in Florida. Honestly without knowing your exact base, and who you are targeting it would be hard to truly comment on the feasibility of that base/area. Every community has very different rules along with the different schools and TDYS. That being said, there is ALOT more into this world than just filling 6 RANDOM dudes in a house.
Here are some things to think of. Do you have military or DOD experience in THIS community you are trying to break in. Do you understand military unwritten rules, your demographic, where the family is located, etc? What do people want to pay? It is great that they get $60 a day but in my experience the lodges and inns are this price. Our area only has one hotel, but in other area there are executive suites that are cheaper than the $420 a week you mentioned. So why would they share a house instead of staying at the lodger or hotel of rate same price.
The military world has TONS of unwritten rules. I can tell you that I own 5 houses in central california nearby a large naval air station and this model doesn't work there. My husband does a tdy where he is gone for 3 weeks every 6 weeks to the same place. I have looked at buying down there and so far it doesn't make sense because of THEIR rules for that TDY.
I know you say that there is at least 15 houses that does this and there is room for competition. You mention not having the ability to book online as a negative. Honestly I can tell you my husband would never book some place like this online! I only say to make sure that these houses have truly not capitalized on everything possible! As that is not a positive in my husband's book :) .
That being said, I agree with @J Martin. I would not buy a house that is soley based on this model. It is way too IFFY. I was working Ft Lee in 2011 with a large apartment company who almost lost their shirt over a army per diem change because more than 50% of their group was based on army off base rules.
I do have furnished rentals near a military base. These were rental that I had already owned and I added furniture. I saw a market needed and I capitalized on it. So I get what you are trying to do. I will be honest and say that military is not my target at all for my rentals!
If I can help please let me know. I can definitely walk you through furnishing etc. I just did a blog post on how I furnish my 2,000 sqft 4 bedroom 2 bath houses for less than 4k. That is with me being 1,000 miles away so include labor for someone else doing it. So I understand on how to furnish houses for corporate rentals, nice but cheap.
Feel free to pm me if you want to talk off line or I can help in any way.
Good LUCK!