I'm Rob. I am a Brit but have lived in the US for 36 years...
Welcome to the forum, Rob.
It's probably important in some conversations/situations that you clarify your passport status.
For instance, a UK citizen has an automatic 45 day visa exemption right that's not available to US passport holders.
I don't know much about Da Nang other than what I have learned from watching practically all the videos on YouTube. I love beach life and I know I am going to love it there.
Read up on life here in Đà Nẵng during the off season, when monsoon winds significantly change "beach life" here.
1. Is there such a thing as a self-storage facility in Da Nang? I want to ship out some of my belongings. I think they would fit in a 4' x 4' x 8' crate but the only places I could find online took small items like luggage. I want to store the crate until I secure a house I like. That may take a month or two.
Best bet is to engage a Vietnamese shipping agent here (many on Face.book) and inquire as to their storage policies following delivery
2. I understand that you can get a tourist visa for 3 months but have to leave the country every 90 days. How difficult is that to get back in? Obviously, if I have a house and belongings, I want to make sure I can get back in the country
Not difficult at all to get back in the country if your immigration record is clear, though without the assistance of an agent, you'll likely be spending 4 to 7 days waiting for your new evisa to be approved after you leave Vietnam.
(A few people are still reporting successfully applying for their next visa by themselves while still in VN, but many are reporting their applications being rejected.)
If you can afford it, I highly recommend planning a 1-week (or longer) vacation in Thailand or Cambodia or Laos or Kuala Lumpur or Singapore or the Philippines once every 3 months.
Currently, most agents have stopped helping foreigners INSIDE Vietnam get their next evisa approved.
The main visa agent in Danang is now reported to be charging $200+ USD to GUARANTEE your next visa will be approved, making it possible for you to do a quick, out-and-back visa border run.
But a border run from here is an all day affair.
There's recently been a TON written about the evisa situation in the forum, so please do some searching, especially in our sticky threads.
I cannot see myself fully retiring. I would like to get involved with a business there. Possibly a partnership if I find the right opportunity or start my own thing. It could be as simple as a clothing store or coffee shop, also considering real estate investing. If you have any insights into these things, I would love to chat.
-@uk2la89
Vietnam forum expert Aidan can share a thread he wrote a while back concerning property laws here.
My personal recommendation is to open a cafe that shares space with a specialty grocery store.
The penultimate example I've seen of such a successful business elsewhere in VN is the Annam Gourmet chain of stores.
Đà Nẵng really doesn't have anything like that.
I don't want to chat in private messages but keep posting your questions (after doing some more research for previous answers in the forum) and I'll do my best to assist when able.
Cheers!