Yes, the entire $10,000 loss can be taken in 2020, since you are active in the partnership. The net loss will be reported on line 1 of the K-1 (form 1065). TurboTax will put it in part II of Schedule E.
I you have a profit, on your next spec house, in this partnership, it too will be treated as ordinary income and not capital gains. It may be subject to self employment (social security and Medicare) tax, as well as income tax. Being salaried at your regular job does not exempt you from having to treat side gig income as self employment.
"I had read somewhere that losses were limited to $3,000 per year on investments". That limit applies to capital losses. Not applicable in your case. Even then, the excess loss is carried forward to the next tax year. See the discussion at the previous link provided., as to whether you treat the income as business profit/loss or a capital gain/loss.
