Opening Record Store

You asked for "tips". I partnered to have owned 3 hi-fi stores getting out in 2001 after 30 yrs of doing it.
Although your store is simpler in product, the thing that you must watch for is "expense creep". You will own the business. Are also owning the building or is he?
Rent can go up, Business regulations met such as fire code and equity clauses. You may be strapped to install the latest fire suppression or widen doorways for handicap access that the owner may apply to you in some fashion.
Differentiated tax codes. State regulations as they apply to transfer of ownership clauses.
New regulations as they apply to sq footage of stores.
10K seems fair to me but I would stipulate payment on a royalty basis to prove how valuable his customer base is within the area itself. If he is "re-opening" somewhere else, he is basically taking his customer base with him if most of his sales are on-line.
I may have missed some stuff but you get the idea.
The killer is in the details....and "customer count".

The Analog Room? I’m hoping a new record shop with higher end jazz and classical lands there. We don’t have many places in the South Bay for that stuff, which is weird given the demographics of the region. 

@fromunda 

Sorry in advance if these items are old news to you, I’m just trying to help....

I think putting together a business plan would be time well spent. Working the details out will require you determining profit margins, expenses, and what your breakeven would be in order to make a profit and perpetuate the business. 
Couple of questions/ comments:

1. If you open a business can you capture the customer base without his location, etc? What are you really gaining? 
2. When you figure your profit model, use numbers that reflect an inventory you don’t already own. That should give you a more realistic idea of your cost of goods. 
3. A good, thorough, business plan template will walk you through items to consider. It will be time consuming but worthwhile work. If you struggle with the business plan and hate the process, business ownership may not be for you. 
4. A friend of mine sold many albums in flea markets, music stores, etc. He dealt with stealing, people took advantage of his good nature regarding quality, sometimes swapping their poor album into a sleeve and taking his 33. Video cameras slowed the shenanigans...

5. Ask to see the guy’s books. He should be able to show you balance sheets, statements of revenues and expenditures, and past tax returns.  This is generally required by someone purchasing a business to determine a fair price to pay. His books will also give you an idea of his expenses like utilities, advertising, insurance, salaries and wages if any, and some yet to be determined. 

To be a great deal it should capture your heart and your head. If the numbers don’t make a compelling case, consider waiting for an opportunity that does.

Best-

My advice is to carry out DUE DILIGENCE!

How many stock items are in the store? Will it attract enough turnover?

Could you put stock online or on Discogs?
🇦🇺

I don’t understand why you’d need to pay anything.
If you're changing the name, there will be no follow
through whether you pay him or not.
Does he own the building? If so then pay him rent.
If he doesn’t, cut a deal with the real owner of it.
Then you are looking at paying $10k for good will
and a customer list. If you can rent that location,
or one close by, his old customer base will find you
without you needing to spend $$ as he is no longer
in business in that area.