I invest in merchandise I can find locally (camera/filming equipment, IT equipment, inventory liquidations, video games, audio equipment etc.) purchasing from auctions and locals looking to sell and then sell the merchandise on my eBay or Amazon store.

I have a very strong and successful background in Real Estate, Fleet Renewal, Visual Merchandising and Entertainment. 

Hence gift cards for book stores, movies, spas, restaurants, electronics stores etc. all score highly while gift cards for grocery stores, hardware stores or mass merchandisers such as Wal-Mart would have less of an effect.

The issue with using Venmo is that it specifically says in the terms of service that it is not to be used for payment of goods or services unless you are an approved vendor.https://help.venmo.com/hc/en-us/articles/217532097-Can-I-use-Venmo-to-buy-or-sell-merchandise-goods-or-services-As with all things, it won't be a problem....until it is. 

Plus, you can avoid the 10% Cook County general merchandise sales tax by buying online.You can purchase an Amazon "Prime" membership for $79 a year.

Whether we're talking about socks or stocks, I like buying quality merchandise when it is marked down." and "It's far better to buy a wonderful company at a fair price than a fair company at a wonderful price."

https://venturebeat.com/2017/11/06/google-and-salesforce-sign-massive-strategic-partnership/Exceptions to the Contractor/Vendor RuleYou do not have to issue 1099-MISC forms to C- and S-corporations or to entities from whom you purchase products, such as merchandise you'll later resell.Payments made to contractors and vendors by debit card, credit card or through third parties like PayPal are also exempt—the IRS uses a different method to track these transactions. 

We were happy to accept the vouchers recently because we realized it opened up a stable funds source for a tenant base that is likely to be rocky in any other case.At the end of the day, it all depends on your merchandise.

Should I have Dan's company bill me for the work or should I just pay for the merchandise and the subcontractors?

Because this is different from building materials in that the HVAC contractor is going to be an authorized dealer for that equipment and not simply a 3rd party going to a materials supplier for merchandise.