We were supposed to close Sept 7th but the buyers’ insurance and Title Company put the brakes on the sale until after Irma passes.

4) pointers to agents/brokers that focus in investment buyers in the area that may have a good track record and solid contacts?

Why not rent it out for one year, then when the lease expires, get the property in mint condition and sell it to a retail buyer? 

And regarding the property itself, if that was truly that great of a deal, wouldn't the seller also know it, or the seller get a realtor to tell them that, or a retail buyer see the listing and know that.

they are all competing or fishing out of the same pond for the buyers.. find a company you like and and work with those that you feel you have the best connection with .. this is important.also there is a very FEW companies that do what I call turn key light..

It has tenants, I have had one month of vacancy since 2012, I would prefer to sell it without an agent, however I worry that there will be dozens of investors wanting to walk through the place, disturbing my tenants, making them antsy and the investors then low ball or otherwise do not generate reasonable offers.What is the best strategy for making sure the potential buyers are serious before letting them in? 

And the seller would have to report any capital gain on their taxes for that year But since he has renovated the place from top to bottom he would fall into the "significant renovation" rule and if a traditional buyer bought the house for 200,000 then the buyer would also have to pay 30,000 in HST?

One way or another, and if nothing else, someone has to evaluate the property as to the probable cost to bring it to an after-repair-value that matches the surrounding market's fair market value for comparable properties - before ever offering to buy it at "such a ridiculously low price" (as the seller will term your offer at first), let alone, before offering to sell it at "wholesale" to your buyer (i.e., so far below fair market price at retail that the repairs can be covered as well as your profit and the flipper's profit in its eventual retail sale -- or 'buy-and-hold-to-rent-out'er's profit before they would expect to get it rented -- plus the title search, closing, and any tax costs related to your purchase from the seller (usually split somehow) - and finally, the title search, closing, and any tax cost split with whoever buys it from you.Now, that someone could be you (you do trust you and your repair-estimate abilities, don't you?)

@Lamont B. any credible HML should be able to provide you with a loan pre-qualification letter to submit with your offer, which is what any other conventional lender would provide to an owner occupant/retail buyer.

People repair their homes all the time before a sale at the request of the buyer.