Deals are out there. I think for $5,500 you couldn’t go wrong. Like others say at $6,500 you would be fighting to make a big enough profit to justify the investment, storage, title transfer fees, etc.
I bought a 2003 100th anniversary Electra Glide for $4,000 a few months ago. Guy bought it as his first bike and was scared of it and wanted out. If your patient deals do come around. But since you mentioned you have flipped bikes in the past you know this all too well.
I would personally stick to flipping metric bikes. A few months ago I purchased a 2001 Roadstar for $1,100. Sold the accessories off of it for around $700 in total. And just sold the bike for $1600. Not a huge profit but a quick one. Problem with buying Harleys is production. There might be 15 Roadstars for sale but at the same time there are 50 Road kings for sale. And all of them are low miles because nobody actually rides their Harley haha
So buyers have more to choose from. JMHO