CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2018
Cash flows from operating activities
Net income	$ 48,508	$ 37,263	$ 1,946
Adjustments to reconcile net income to net cash provided by (used in) operating activities:
Depreciation and amortization	3,249	2,682	1,685
Equity-based awards	2,213	154	154
Loss (gain) on asset disposals	10	1,371	(49)
Change in fair value of long-term warrant liability	(771)	(1,336)	33,187
Loss (gain) on extinguishment of debt	6,559	0	(209)
Non-cash interest expense	477	3,478	2,441
Deferred income tax provision	509	0	0
Loss (gain) on contingent consideration	5,520	(1,674)	0
(Increase) decrease in assets:
Accounts receivable	(3,185)	(2,344)	(4,743)
Inventories	127,214	(38,954)	(39,858)
Prepaid expenses and other current assets	(7,984)	(5,565)	111
Deposits	(5)	2	(49)
Increase (decrease) in liabilities:
Accounts payable	7,235	(966)	11
Other payables and accrued expenses	10,528	614	1,605
Customer deposits	12,400	(450)	(482)
Net cash provided by (used in) operating activities	212,477	(5,725)	(4,250)
Cash flows from investing activities
Purchases of property and equipment and construction in progress	(6,309)	(7,291)	(10,135)
Proceeds from disposal of property and equipment	1,637	73	0
Proceeds from sale and leaseback	0	15,623	0
Cash used in acquisitions	0	(19,403)	(13,785)
Net cash used in investing activities	(4,672)	(10,998)	(23,920)
Cash flows from financing activities
Net (payments) borrowings from floor plan	(101,342)	24,401	35,421
Net payment to related party	0	0	(300)
Proceeds from long-term debt	129,306	13,801	7,046
Payments on long-term debt	(121,800)	(9,942)	(3,899)
Payments of debt issuance costs	(3,910)	(203)	(662)
Payments of debt extinguishment costs	(4,207)	0	0
Payments of offering costs	(5,646)	(1,148)	0
Payments of preferred issuance costs	0	0	(93)
Payment of acquisition contingent consideration	(1,456)	0	0
Distributions to redeemable preferred interest members and redemption of redeemable preferred interest	(90,503)	(3,364)	0
Proceeds from issuance of Class A common stock sold in initial public offering, net of underwriting discounts and commissions	59,234	0	0
Proceeds from issuance of Class A common stock sold in September offering, net of underwriting discounts and commissions	8,075	0	0
Distributions to members	(18,895)	(11,087)	(3,256)
Net cash (used in) provided by financing activities	(151,144)	12,458	34,257
Net change in cash	56,661	(4,265)	6,087
Cash and restricted cash at beginning of period	11,492	15,757	9,670
Cash and restricted cash at end of period	68,153	11,492	15,757
Supplemental cash flow disclosures
Cash paid for interest	17,212	12,485	6,929
Cash paid for income taxes	246	0	0
Noncash items
Acquisition purchase price funded by long-term debt	0	18,800	9,000
Acquisition purchase price funded by seller notes payable	0	10,438	3,042
Acquisition purchase price funded by contingent consideration	0	0	2,644
Purchase of property and equipment funded by long-term debt	1,190	1,067	0
Offering costs, accrued not yet paid	$ 430	$ 1,500	$ 0