As soon as you get an offer accepted, rescind the others.

My current lender only offers primary residence HELOCs, but is currently not accepting applications (assuming they will be by next summer). 

Challenge accepted @Gorden Lopes!

Hosts who don’t complete this requirement before the deadline may be unable to accept new reservations.

I ran into that problem multiple times where I put in a bid a few thousand less than asking price that I KNEW they would accept, only to have an out of state investors blow my offer out of the water. 

@John B.An escalation clause would up your offer up to a certain amount (think eBay).If your offer is accepted the seller would need to show the offer you beat.

IMO your options are: (1) look in less expensive markets where your dollar goes further, (2) invest in a different asset type, (3) invest with someone else / partner on a deal, (4) wait for prices to adjust, if it happens... personally, I would expect to see some distressed sellers who are going to be taken out by the eviction moratoriums due to abusive tenants - MA is brutal when it comes to the super-progressive lawmakers who think free rent w/o aid to landlords is perfectly acceptable... but I digress.

I know typically with courthouse auctions it is a very quick turnaround (maybe 24 hours) from when your offer gets accepted to when the payment is due and you close so you will have to be comfortable with the added risk of not being able to do much due diligence, or will have to scramble to quickly verify you are buying a clean title and to produce the cash for purchase if you don't have it already liquid.

That isn't to say that isn't what the house is worth, but most sellers aren't going to accept that. 

The discount needed is usually not something the seller is willing to accept, at least at this point.