There are or there is??grammar confusion

The object of the verb is 'lots of money'. 'Lots' looks like a plural noun but it is an idiom - 'lots of' = 'a large amount of' - and an adjective and whether it is singular or plural depends on the noun it qualifies. In this case 'money' is a singular collective noun, so "There is [lots of] money under the sofa" is correct. On the other hand, you should say "There were lots of people" or "lots of coins" or "lots of banknotes", since people, coins and banknotes are 'numerable'. In fact, 'lots of' is generally thought of as a colloquial expression and should be avoided in formal English. The correct meaning of 'a lot' is a 'collection' or a 'parcel of things taken together'. It is often used in auctions or sales when the buyer bids or pays a certain amount for a 'lot' or collection of items. Of course, it can also be used in the plural "There were several lots of antique clocks in the auction".

"Is" is the right answer. There is lots of money under the sofa. We use "there is" for uncountable nouns such as sugar, water, money, etc." We use "there are" for countable nouns such as bags, computers, desks. "Lots of" or "a lot of" are just used as quantifiers. They mean the same and they can be used with countable and uncountable nouns.

Some of the language rules are not so simple to understand. People who have a different native language(or mother tongue) do find difficulty in understanding these rules. Yet, do not despair. There is always scope of improvement as I myself have learnt!