I've been looking at picking up houses through the auction sites (Hubzu, Auction.com, etc) and I know that as the buyer I will be responsible for closing costs.

Hopefully, its market favors sellers over buyers in that area you are looking at investing in. 

If an investor is eager to pay 350K all-cash off market, I'll bet you can find a retail buyer (or an unsophisticated "investor") to pay even more.

If I'm virtually wholesaling from out the country how do I go about obtaining the key for the property so that I can give my buyers access to the property?

It may work out, but I feel like more often than not your buyer would go over budget, and your business would suffer from selling bad leads.

Do you think this is positive for a rental investor as higher rates may make ownership costs higher for some buyers thus increasing rents?

This ends up being the same thing financially in the end for the buyer if they end up exercising their option to buy.As the seller, this ends up netting out the same as rent credits...if the buyer exercises their option.Now, if the buyer doesn't exercise their option, the seller gets full income from the full rent each month.

I have a couple properties that need buyers.

Greetings, CO newbie jumping into SFR investing while working a FT job.  Do I have to inform the seller that I intend to use the property as a rental property when submitting a purchase offer for it?  Thanks in advan...

Wholesalers keep a list of buyers and will email out any properties that they have available.