Yr Egin, being built in Carmarthen by University of Wales Trinity St David, will be ready in late spring 2018.
University chiefs told the Welsh Affairs committee they hoped the site would ultimately be oversubscribed.
Vice-chancellor Medwin Hughes said he hoped Yr Egin would reach 60% capacity within the next two months but conceded it would need more companies on board.
"The £3m of upfront rent from S4C helps with cash flow for two to three years but we could need more than 60% capacity to break even," he told the committee on Monday.
As part of its contract with the University, S4C will also be paying £60,000 in annual service charges.
Brecon and Radnorshire Conservative MP Chris Davies told the committee there had been an "untidy smell around" the project and "a fog" surrounding the relationship between the university and the Welsh-language broadcaster.
Mr Hughes denied it, saying: "There has been a clear and consistent message between S4C and the University.
"As with any large agreement there are confidentiality agreements.  In the main, the engagement between S4C and the University has been presented in an appropriate manner."
MPs had summoned university leaders amid concern over a gap in funding gap for the project.
Earlier in March the Welsh Government committed £3m with after the University realised that the amount of European funding available to them would not be enough.
In February, First Minister Carwyn Jones told AMs that S4C promised that the move from Cardiff would be at no cost to the taxpayer.

Thousands of people worked at its Merthyr Tydfil washing machine plant over 60 years. It stopped production in 2009 but a warehouse still operates.
The company will contribute £60m to the pension scheme.
The Pensions Regulator has approved the proposal and the scheme is expected to transfer into the Pension Protection Fund (PPF).
The deal has been struck because there was "clear and extensive evidence" that Hoover would inevitably fall into insolvency otherwise.
The regulator said it was the "best possible outcome for members in challenging circumstances".
Up to 4,000 people in Wales could be affected. Those still under retirement age could receive an immediate 10% cut in their pension pot.
The pension scheme has 7,500 members, made up of 5,319 pensioners and 2,184 who have deferred their pensions.
A distribution warehouse and head office is still based at Pentrebach in Merthyr.
At about £500m, the pension scheme is roughly the same size as collapsed store group BHS's scheme. That is still being assessed for take-over by the PPF, which acts as a pensions "lifeboat".
The Hoover pensions scheme will also receive a shareholding worth a 33% stake in the company as part of the deal.
The scheme has a deficit of about £250m and Hoover had to prove the business was at risk of going bust in the next 12 months unless action was taken.
Nicola Parish, of The Pensions Regulator, said: "We do not agree to these types of arrangements lightly but in this case we believe it is the right outcome for scheme members and the PPF."
She said this type of pension restructuring was rare and guidelines were in place to the arrangements were "not abused by businesses seeking to offload their pension liabilities".
This is the first such deal approved in 2017 and only the second in the last two years.
Hoover is a century-old household appliances brand but has been owned by Italian firm Candy for more than 20 years.
The building which will be S4C's new headquarters has no other tenants signed up yet, MPs have been told.
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A deal has been struck for Hoover to move the company's pension scheme into a protection fund.