Tottenham Hotspur Football and Athletic Company Limited was a Private Company at the time and it was difficult for anyone new to buy shares. Indeed when Irving Scholar bought the Club in the early eighties and made it public, he used the ruse of buying proxies for the votes at the AGM to get the board out and take over the Club, because he couldn't buy up the shares initially.
The shares had rarely changed hands and the shareholders tended to be the same for decades. They don't appear to have put any new money into the club at all by loan or new shares. For successful clubs like Spurs with a capacity of about 68,000 at the time, though the ground rarely had that many in, c 45,000 was all you'd get for most games, it was a licence to print money, because between about 1934 and the late sixties very little was done to the ground and facilities, though to be fair, the club did invest in a new training ground in Cheshunt in the 1950's and money was spent on floodlights in the mid to late 50's. Shareholders were not there to take money from the club but for the kudos within the community. So the excess of income over costs either sat in the bank or was used to buy new players. Up to 1961 players were on a maximum of £20 per week in the season and £10 pw in the summer. In the early sixties this didn't change too much, though there was great publicity when Tommy Trinder, the Chairman of Fulham made Johnny Haynes the first £100 per week footballer in England. Even in the early seventies players were getting second jobs, some for example as driving instructors (John Tudor of Saudi Sportswashing Machine comes to mind), to supplement their income. So those with money could spend it on transfer fees. In the sixties Tottenham had the reputation as the "Bank of England" club for this reason, as Everton and Sunderland had in previous decades.
So: Gate receipts.