Maybe they are offering financing because no traditional lender will lend on the building. 

I've done a lot of wraps and subtos and highly prefer the seller-finance strategy for a lot of reasons, including offering the opportunity of homeownership to those otherwise rejected by traditional banks.

I have a HELOC on my Texas primary residence and am considering a house hack for my next purchase.

I have spoken to lenders about traditional financing and also DSCR loans.

Quote from @Matt Wan: Can I purchase a property using a traditional mortgage without being physically present for any part of the process?

I worked with a travel nurse who does shift work and 5 lenders said that they couldn’t finance her primary residence purchase and I ended up making it happen for her. 

What do you mean by "traditional 6-month financing route"?

Quote from @Karen Smith: With more investors turning to private money lenders for faster funding, what benefits have you seen from using private financing versus traditional bank loans? 

My wife and I have obtained three traditional loans and one lease with the option to purchase, resulting in most banks turning us down based on debt to income (non-portfolio lenders). 

The crypto can be considered as EMD or down payment, the rest of the transaction will happen just as if you were running a traditional transaction.If a seller is completely against the idea of receiving crypto, you can always use a service like Bitpay to convert the cryptocurrency to cash.Last but not least, I always ask clients... why sell your crypto asset when you use it to secure a loan?