He does not need my money in that he has other options. 

A lot of options and it depends on your goals.

Most though will have a due date in the beginning of the year such that you have the option of paying it in the prior year.

These are the options I've thought of:a.

By simply making the requirement to make vacant for closing alone with typical "time of the essence" language the buyer has the option to walk away if the seller hasn't met their obligation but can also hold the seller to the contract or work the deal further.

To sue is the only option, that gets expensive and takes months...Spoke with our attorney this morning and sent him everything.

Is an ADU (accessory dwelling unit) in option for your home?

5% down conventional financing is probably your best option but you can consider FHA as well.

Probably your best option will be to make some improvements, (maybe not the full $450k but enough to make it sell for as close to top dollar as possible without over-spending on improvements), and your 2nd best option is to sell it "as-is" for an appropriate price given the current condition.

Also, depending on the purchase timeline, exploring a delayed purchase refinance could be a viable option.