I don't understand how that is different to any spouse applying for FLR?
Someone applying for FLR(M) will still have a valid visa to work in the UK on the date they apply, and that visa will be extended while the FLR(M) is processing, even if it expires.
However, the OP said they would only have the right to work in the UK as self-employed until August 1st 2018, but that they were applying for the spousal visa in August... which implies that the visa will run out and they will have to return to the US to apply. If that is the case, their UK income would not be considered anway because on the date of application, they will not have a valid visa to work in the UK.
The things you have to show for self-employment - which is an extremely tricky category to qualify for due to the restrictions and sheer number of documents required - are:
- right to work in the UK on the date of application
- a total of £18,600 earned in the last FULL financial year (usually April to April) - with tax returns to back it up
and
- evidence that the self-employment income is ongoing and will continue after the visa application has been lodged
The OP will not likely be able to show either of these because:
a) if the financial year runs April to April, they will not have a full financial year of self-employment income to show by August 2018
and
b) it sounds like they will no longer have a visa that allows them to continue earning self-employment income in the UK after 1st August 2018
We had someone refused their FLR(M) last year because they set up their company on October 31st 2015, but applied for their visa on October 30th 2016... it was an automatic refusal because they had not been self-employed for a full year on the date of application. If they had applied just one day later, their visa may well have been granted.
Someone else also got refused because although they had been self-employed for more than 2 years and were using the average of the last 2 years of income (Category G), they had switched their self-employment type (i.e. sole trader to limited company) 2 months before the end of the tax year (in Feb). Because they switched mid-financial year, they no longer qualified for the visa, because they did not have a full financial year of income as a limited company... they only had a few weeks of income. Due to the self-employment type switch in February 2016, they would not actually qualify for the visa until the end of the NEXT financial year, in April 2017.