Faced with a third, hefty rent increase in scarcely two years, a majority of the tenants of Middlebrook Mobile Home Park in Germantown had placed their April rent into an escrow account in a move designed to convince their landlord to scale back the latest increase.

The tactic, combined with the opening of an investigation into the business practices of Middlebrook by Montgomery County's Office of Landlord-Tenant Affairs, apparently worked.

Middlebrook's owner, Kamakoti Investors Limited Partnership, has agreed to reduce the size of the rent increases to 8 1/2 percent--Montgomery County's voluntary guideline--from a 19.4 percent boost for many tenants, and to stick to whatever is the county's guideline in the future, according to Elsie Jerrell, a Middlebrook tenant. The owner also agreed to eliminate several monthly charges, such as $10 for extra adults and $1 for children--charges that had been imposed on Middlebrook tenants even before Kamakoti took over in 1981.

"We feel very good about this agreement," said Jerrell, who is also president of the Germantown Mobile Home Citizens Association. "We were able to sit down . . . and do something about high rent and the maintenance problems we have in the park."

There are 181 mobile homes in the park.

Edward O. Wayson Jr., attorney for Kamakoti, said the tenants raised some valid points during negotiations. "The decision was that the suggested guideline was a fair barometer, a fair compromise between no increase, which they wanted, and the percentage we asked for."

Wayson said the extra charges were assumed by the investment partnership to be appropriate when it bought the property, but when the County Office of Landlord-Tenant Affairs raised specific questions about them, "We reviewed them and decided that, under county rules, they weren't justified, and we decided to delete them."

Since Montgomery County's rent control law was lifted in 1981, the monthly rents have almost doubled for many of Middlebrook's tenants, who own their own mobile homes but rent ground space, including water and sewer service and trash removal, from the landlord, Jerrell said. The rent for many residents was increased an average of 30 percent initially, about 24 percent the second time, and 19.4 percent most recently, she said.

"We felt the rent hikes were unjustified," she said. "But we have nowhere to go when our rent goes up. The cost of relocating a mobile home is quite expensive, and zoning in Montgomery County doesn't allow us to purchase a lot and put a mobile home on it.

"We can't abandon our mobile homes and move out."

The basic rent for long-time residents of Middlebrook went from an average of $96.50 to $185 with the latest--now reduced--increase, according to Rick Ferrara, executive director of Montgomery County's Office of Landlord-Tenant Affairs.

Some residents who moved in within the last two years came in at higher monthly rents and may be paying more, he added. Wayson noted that the rent increases effective in April were below the 8 1/2 percent guideline for those Middlebrook residents who did move in since 1981.

Ferrara noted that, during his office's investigation, Kamakoti and Sateesh Singh, one of its partners, had been asked to provide all income and expense data and asked for an itemization of all extra charges and the rationale for them. State law requires that fees be related to a specific service or a cost incurred by the landlord, he said.

As an example of a specific complaint on the charges, Ferrara noted that a woman who lives at Middlebrook was charged $10 extra per month for a roommate and $5 for an extra car when she took a roommate after a divorce "even though there was the same number of people and the same number of cars" at the house.

"This type of thing really served to irritate the tenants," Ferrara said.

Wayson, Kamakoti's lawyer, said the owners agreed to eliminate all extra charges, which he called a nuisance anyway, except for those services that cost extra to provide, such as storage for boats and third cars. There never was supposed to be a charge for a second car, and the owners will reimburse anyone for such a charge that may have been imposed, he said.